diff --git a/src/passes/1-parser/cameligo/AST.ml b/src/passes/1-parser/cameligo/AST.ml
index c558eb72d..df94dc783 100644
--- a/src/passes/1-parser/cameligo/AST.ml
+++ b/src/passes/1-parser/cameligo/AST.ml
@@ -166,6 +166,7 @@ and type_expr =
 | TFun    of (type_expr * arrow * type_expr) reg
 | TPar    of type_expr par reg
 | TVar    of variable
+| TStringLiteral of Lexer.lexeme reg
 
 and cartesian = (type_expr, times) nsepseq reg
 
@@ -407,6 +408,7 @@ let type_expr_to_region = function
 | TApp {region; _}
 | TFun {region; _}
 | TPar {region; _}
+| TStringLiteral {region; _}
 | TVar {region; _} -> region
 
 let list_pattern_to_region = function
diff --git a/src/passes/1-parser/cameligo/Parser.mly b/src/passes/1-parser/cameligo/Parser.mly
index 950423005..12352480d 100644
--- a/src/passes/1-parser/cameligo/Parser.mly
+++ b/src/passes/1-parser/cameligo/Parser.mly
@@ -149,6 +149,7 @@ cartesian:
 core_type:
   type_name      { TVar $1 }
 | par(type_expr) { TPar $1 }
+| "<string>"     { TStringLiteral $1 }
 | module_name "." type_name {
     let module_name = $1.value in
     let type_name   = $3.value in
diff --git a/src/passes/1-parser/cameligo/ParserLog.ml b/src/passes/1-parser/cameligo/ParserLog.ml
index 4791ff6dc..6ebe07c73 100644
--- a/src/passes/1-parser/cameligo/ParserLog.ml
+++ b/src/passes/1-parser/cameligo/ParserLog.ml
@@ -156,6 +156,7 @@ and print_type_expr state = function
 | TPar par        -> print_type_par state par
 | TVar var        -> print_var state var
 | TFun t          -> print_fun_type state t
+| TStringLiteral s -> print_string state s
 
 and print_fun_type state {value; _} =
   let domain, arrow, range = value in
@@ -1124,6 +1125,9 @@ and pp_type_expr state = function
  | TVar v ->
     pp_node  state "TVar";
     pp_ident (state#pad 1 0) v
+ | TStringLiteral s ->
+    pp_node   state "String";
+    pp_string (state#pad 1 0) s
 
 and pp_type_tuple state {value; _} =
   let components     = Utils.nsepseq_to_list value.inside in
diff --git a/src/passes/1-parser/pascaligo/AST.ml b/src/passes/1-parser/pascaligo/AST.ml
index 0c26f87cd..fa22a7b25 100644
--- a/src/passes/1-parser/pascaligo/AST.ml
+++ b/src/passes/1-parser/pascaligo/AST.ml
@@ -185,6 +185,7 @@ and type_expr =
 | TFun    of (type_expr * arrow * type_expr) reg
 | TPar    of type_expr par reg
 | TVar    of variable
+| TStringLiteral of Lexer.lexeme reg
 
 and cartesian = (type_expr, times) nsepseq reg
 
@@ -658,6 +659,7 @@ let type_expr_to_region = function
 | TApp    {region; _}
 | TFun    {region; _}
 | TPar    {region; _}
+| TStringLiteral {region; _}
 | TVar    {region; _} -> region
 
 let rec expr_to_region = function
diff --git a/src/passes/1-parser/pascaligo/Parser.mly b/src/passes/1-parser/pascaligo/Parser.mly
index 1c31f92cd..21d9420b7 100644
--- a/src/passes/1-parser/pascaligo/Parser.mly
+++ b/src/passes/1-parser/pascaligo/Parser.mly
@@ -161,6 +161,7 @@ cartesian:
 
 core_type:
   type_name      { TVar $1 }
+| "<string>"     { TStringLiteral $1 }
 | par(type_expr) { TPar $1 }
 | type_name type_tuple {
     let region = cover $1.region $2.region
diff --git a/src/passes/1-parser/pascaligo/ParserLog.ml b/src/passes/1-parser/pascaligo/ParserLog.ml
index 0467d7a61..6347b07f7 100644
--- a/src/passes/1-parser/pascaligo/ParserLog.ml
+++ b/src/passes/1-parser/pascaligo/ParserLog.ml
@@ -153,6 +153,7 @@ and print_type_expr state = function
 | TFun    type_fun    -> print_type_fun    state type_fun
 | TPar    par_type    -> print_par_type    state par_type
 | TVar    type_var    -> print_var         state type_var
+| TStringLiteral s -> print_string state s
 
 and print_cartesian state {value; _} =
   print_nsepseq state "*" print_type_expr value
@@ -940,6 +941,9 @@ and pp_type_expr state = function
                     field_decl.value in
     let fields = Utils.nsepseq_to_list value.ne_elements in
     List.iteri (List.length fields |> apply) fields
+| TStringLiteral s ->
+  pp_node   state "String";
+  pp_string (state#pad 1 0) s
 
 and pp_cartesian state {value; _} =
   let apply len rank =
diff --git a/src/passes/10-transpiler/transpiler.ml b/src/passes/10-transpiler/transpiler.ml
index 7168af974..3949f34ff 100644
--- a/src/passes/10-transpiler/transpiler.ml
+++ b/src/passes/10-transpiler/transpiler.ml
@@ -258,10 +258,6 @@ let rec transpile_type (t:AST.type_expression) : type_value result =
       ok (T_big_map kv')
   | T_operator (TC_map_or_big_map _) ->
       fail @@ corner_case ~loc:"transpiler" "TC_map_or_big_map should have been resolved before transpilation"
-  | T_operator (TC_michelson_or {l;r}) ->
-      let%bind l' = transpile_type l in
-      let%bind r' = transpile_type r in
-      ok (T_or ((None,l'),(None,r')))
   | T_operator (TC_list t) ->
       let%bind t' = transpile_type t in
       ok (T_list t')
@@ -276,9 +272,7 @@ let rec transpile_type (t:AST.type_expression) : type_value result =
       let%bind result' = transpile_type result in
       ok (T_function (param', result'))
     )
-  (* TODO hmm *)
-  | T_sum m ->
-      let is_michelson_or = Ast_typed.Helpers.is_michelson_or m in
+  | T_sum m when Ast_typed.Helpers.is_michelson_or m ->
       let node = Append_tree.of_list @@ kv_list_of_cmap m in
       let aux a b : type_value annotated result =
         let%bind a = a in
@@ -286,14 +280,22 @@ let rec transpile_type (t:AST.type_expression) : type_value result =
         ok (None, T_or (a, b))
       in
       let%bind m' = Append_tree.fold_ne
-                      (fun (Ast_typed.Types.Constructor ann, a) ->
-                        let%bind a = transpile_type a in
-                        ok ((
-                          if is_michelson_or then 
-                            None 
-                          else 
-                            Some (String.uncapitalize_ascii ann)), 
-                          a))
+                      (fun (_, ({ctor_type ; michelson_annotation}: AST.ctor_content)) ->
+                        let%bind a = transpile_type ctor_type in
+                        ok (michelson_annotation, a) )
+                      aux node in
+      ok @@ snd m'
+  | T_sum m ->
+      let node = Append_tree.of_list @@ kv_list_of_cmap m in
+      let aux a b : type_value annotated result =
+        let%bind a = a in
+        let%bind b = b in
+        ok (None, T_or (a, b))
+      in
+      let%bind m' = Append_tree.fold_ne
+                      (fun (Ast_typed.Types.Constructor ann, ({ctor_type ; _}: AST.ctor_content)) ->
+                        let%bind a = transpile_type ctor_type in
+                        ok (Some (String.uncapitalize_ascii ann), a))
                       aux node in
       ok @@ snd m'
   | T_record m ->
@@ -368,7 +370,8 @@ and transpile_environment_element_type : AST.environment_element -> type_value r
 
 and tree_of_sum : AST.type_expression -> (AST.constructor' * AST.type_expression) Append_tree.t result = fun t ->
   let%bind map_tv = get_t_sum t in
-  ok @@ Append_tree.of_list @@ kv_list_of_cmap map_tv
+  let kt_list = List.map (fun (k,({ctor_type;_}:AST.ctor_content)) -> (k,ctor_type)) (kv_list_of_cmap map_tv) in
+  ok @@ Append_tree.of_list kt_list
 
 and transpile_annotated_expression (ae:AST.expression) : expression result =
   let%bind tv = transpile_type ae.type_expression in
diff --git a/src/passes/10-transpiler/untranspiler.ml b/src/passes/10-transpiler/untranspiler.ml
index a2c2f79d9..a727eedff 100644
--- a/src/passes/10-transpiler/untranspiler.ml
+++ b/src/passes/10-transpiler/untranspiler.ml
@@ -185,18 +185,6 @@ let rec untranspile (v : value) (t : AST.type_expression) : AST.expression resul
         bind_fold_right_list aux init big_map'
       )
     | TC_map_or_big_map _ -> fail @@ corner_case ~loc:"untranspiler" "TC_map_or_big_map t should not be present in mini-c"
-    | TC_michelson_or {l=l_ty; r=r_ty} -> (
-        let%bind v' = bind_map_or (get_left , get_right) v in
-        ( match v' with
-          | D_left l  ->
-            let%bind l' = untranspile l l_ty in
-            return @@ E_constructor { constructor = Constructor "M_left" ; element = l' }
-          | D_right r ->
-            let%bind r' = untranspile r r_ty in
-            return @@ E_constructor { constructor = Constructor "M_right" ; element = r' }
-          | _ -> fail (wrong_mini_c_value "michelson_or" v)
-        )
-      )
     | TC_list ty -> (
         let%bind lst =
           trace_strong (wrong_mini_c_value "list" v) @@
@@ -232,7 +220,7 @@ let rec untranspile (v : value) (t : AST.type_expression) : AST.expression resul
       fail @@ bad_untranspile "contract" v
   )
   | T_sum m ->
-      let lst = kv_list_of_cmap m in
+      let lst = List.map (fun (k,{ctor_type;_}) -> (k,ctor_type)) @@ kv_list_of_cmap m in
       let%bind node = match Append_tree.of_list lst with
         | Empty -> fail @@ corner_case ~loc:__LOC__ "empty sum type"
         | Full t -> ok t
diff --git a/src/passes/2-concrete_to_imperative/cameligo.ml b/src/passes/2-concrete_to_imperative/cameligo.ml
index 933909e65..d8984bb50 100644
--- a/src/passes/2-concrete_to_imperative/cameligo.ml
+++ b/src/passes/2-concrete_to_imperative/cameligo.ml
@@ -160,6 +160,10 @@ open Operators.Concrete_to_imperative.Cameligo
 
 let r_split = Location.r_split
 
+let get_t_string_singleton_opt = function
+  | Raw.TStringLiteral s -> Some (String.(sub s.value 1 ((length s.value)-2)))
+  | _ -> None
+
 let rec pattern_to_var : Raw.pattern -> _ = fun p ->
   match p with
   | Raw.PPar p -> pattern_to_var p.value.inside
@@ -236,12 +240,29 @@ and compile_type_expression : Raw.type_expr -> type_expression result = fun te -
   | TApp x -> (
       let (x,loc) = r_split x in
       let (name, tuple) = x in
-      let lst = npseq_to_list tuple.value.inside in
-      let%bind lst' = bind_map_list compile_type_expression lst in
-      let%bind cst =
-        trace (unknown_predefined_type name) @@
-        type_operators name.value in
-      t_operator ~loc cst lst'
+      ( match name.value with
+        | "michelson_or" -> 
+          let lst = npseq_to_list tuple.value.inside in
+          (match lst with
+          | [a ; b ; c ; d ] -> (
+            let%bind b' =
+              trace_option (simple_error "second argument of michelson_or must be a string singleton") @@
+                get_t_string_singleton_opt b in
+            let%bind d' =
+              trace_option (simple_error "fourth argument of michelson_or must be a string singleton") @@
+                get_t_string_singleton_opt d in
+            let%bind a' = compile_type_expression a in
+            let%bind c' = compile_type_expression c in
+            ok @@ t_michelson_or ~loc a' b' c' d'
+            )
+          | _ -> simple_fail "michelson_or does not have the right number of argument")
+        | _ ->
+          let lst = npseq_to_list tuple.value.inside in
+          let%bind lst' = bind_map_list compile_type_expression lst in
+          let%bind cst =
+          trace (unknown_predefined_type name) @@
+          type_operators name.value in
+          t_operator ~loc cst lst' )
     )
   | TProd p -> (
       let%bind tpl = compile_list_type_expression  @@ npseq_to_list p.value in
@@ -274,6 +295,7 @@ and compile_type_expression : Raw.type_expr -> type_expression result = fun te -
         @@ npseq_to_list s in
       let m = List.fold_left (fun m (x, y) -> CMap.add (Constructor x) y m) CMap.empty lst in
       ok @@ make_t ~loc @@ T_sum m
+  | TStringLiteral _s -> simple_fail "we don't support singleton string type"
 
 and compile_list_type_expression (lst:Raw.type_expr list) : type_expression result =
   match lst with
diff --git a/src/passes/2-concrete_to_imperative/pascaligo.ml b/src/passes/2-concrete_to_imperative/pascaligo.ml
index e7a99ec7d..e0bccd831 100644
--- a/src/passes/2-concrete_to_imperative/pascaligo.ml
+++ b/src/passes/2-concrete_to_imperative/pascaligo.ml
@@ -142,6 +142,10 @@ let return_statement expr = ok @@ fun expr'_opt ->
   | None -> ok @@ expr
   | Some expr' -> ok @@ e_sequence expr expr'
 
+let get_t_string_singleton_opt = function
+  | Raw.TStringLiteral s -> Some (String.(sub s.value 1 ((length s.value)-2)))
+  | _ -> None
+
 
 let rec compile_type_expression (t:Raw.type_expr) : type_expression result =
   match t with
@@ -162,13 +166,30 @@ let rec compile_type_expression (t:Raw.type_expr) : type_expression result =
   | TApp x ->
       let (x, loc) = r_split x in
       let (name, tuple) = x in
-      let lst = npseq_to_list tuple.value.inside in
-      let%bind lst =
-        bind_list @@ List.map compile_type_expression lst in (** TODO: fix constant and operator*)
-      let%bind cst =
-        trace (unknown_predefined_type name) @@
-        type_operators name.value in
-      t_operator ~loc cst lst
+      (match name.value with
+        | "michelson_or" -> 
+          let lst = npseq_to_list tuple.value.inside in
+          (match lst with
+          | [a ; b ; c ; d ] -> (
+            let%bind b' =
+              trace_option (simple_error "second argument of michelson_or must be a string singleton") @@
+                get_t_string_singleton_opt b in
+            let%bind d' =
+              trace_option (simple_error "fourth argument of michelson_or must be a string singleton") @@
+                get_t_string_singleton_opt d in
+            let%bind a' = compile_type_expression a in
+            let%bind c' = compile_type_expression c in
+            ok @@ t_michelson_or ~loc a' b' c' d'
+            )
+          | _ -> simple_fail "michelson_or does not have the right number of argument")
+        | _ ->
+          let lst = npseq_to_list tuple.value.inside in
+          let%bind lst =
+            bind_list @@ List.map compile_type_expression lst in (** TODO: fix constant and operator*)
+          let%bind cst =
+            trace (unknown_predefined_type name) @@
+            type_operators name.value in
+          t_operator ~loc cst lst)
   | TProd p ->
       let%bind tpl = compile_list_type_expression
     @@ npseq_to_list p.value in
@@ -203,6 +224,7 @@ let rec compile_type_expression (t:Raw.type_expr) : type_expression result =
         @@ npseq_to_list s in
       let m = List.fold_left (fun m (x, y) -> CMap.add (Constructor x) y m) CMap.empty lst in
       ok @@ make_t ~loc @@ T_sum m
+  | TStringLiteral _s -> simple_fail "we don't support singleton string type"
 
 and compile_list_type_expression (lst:Raw.type_expr list) : type_expression result =
   match lst with
diff --git a/src/passes/3-self_ast_imperative/michelson_or.ml b/src/passes/3-self_ast_imperative/michelson_or.ml
deleted file mode 100644
index b8adb0fe8..000000000
--- a/src/passes/3-self_ast_imperative/michelson_or.ml
+++ /dev/null
@@ -1,9 +0,0 @@
-open Ast_imperative
-open Trace
-
-let peephole_type_expression : type_expression -> type_expression result = fun e ->
-  let return type_content = ok { type_content; location=e.location } in
-  match e.type_content with
-  | T_operator (TC_michelson_or (l_ty,r_ty)) ->
-    return @@ T_sum (CMap.of_list [ (Constructor "M_left", l_ty) ; (Constructor "M_right", r_ty) ])
-  | e -> return e
diff --git a/src/passes/3-self_ast_imperative/self_ast_imperative.ml b/src/passes/3-self_ast_imperative/self_ast_imperative.ml
index 5b02d6a49..b0270ebd0 100644
--- a/src/passes/3-self_ast_imperative/self_ast_imperative.ml
+++ b/src/passes/3-self_ast_imperative/self_ast_imperative.ml
@@ -7,7 +7,6 @@ let all_expression_mapper = [
 ]
 let all_type_expression_mapper = [
   Entrypoints_length_limit.peephole_type_expression ;
-  Michelson_or.peephole_type_expression ;
 ]
 
 let all_exp = List.map (fun el -> Helpers.Expression el) all_expression_mapper
diff --git a/src/passes/4-imperative_to_sugar/imperative_to_sugar.ml b/src/passes/4-imperative_to_sugar/imperative_to_sugar.ml
index 527c6ee5b..5f7240b41 100644
--- a/src/passes/4-imperative_to_sugar/imperative_to_sugar.ml
+++ b/src/passes/4-imperative_to_sugar/imperative_to_sugar.ml
@@ -3,6 +3,15 @@ module O = Ast_sugar
 open Trace
 
 module Errors = struct
+  let corner_case loc =
+    let title () = "corner case" in
+    let message () = Format.asprintf "corner case, please report to developers\n" in
+    let data = [
+      ("location",
+      fun () -> Format.asprintf  "%s" loc)
+    ] in
+    error ~data title message
+
   let bad_collection expr =
     let title () = "" in
     let message () = Format.asprintf "\nCannot loop over this collection : %a\n" I.PP.expression expr in
@@ -110,7 +119,8 @@ let rec compile_type_expression : I.type_expression -> O.type_expression result
       let%bind sum = 
         bind_map_list (fun (k,v) ->
           let%bind v = compile_type_expression v in
-          ok @@ (k,v)
+          let content : O.ctor_content = {ctor_type = v ; michelson_annotation = None} in
+          ok @@ (k,content)
         ) sum
       in
       return @@ O.T_sum (O.CMap.of_list sum)
@@ -132,6 +142,13 @@ let rec compile_type_expression : I.type_expression -> O.type_expression result
       return @@ T_arrow {type1;type2}
     | I.T_variable type_variable -> return @@ T_variable type_variable 
     | I.T_constant type_constant -> return @@ T_constant type_constant
+    | I.T_operator (TC_michelson_or (l,l_ann,r,r_ann)) ->
+      let%bind (l,r) = bind_map_pair compile_type_expression (l,r) in
+      let sum : (O.constructor' * O.ctor_content) list = [
+        (O.Constructor "M_left" , {ctor_type = l ; michelson_annotation = Some l_ann}); 
+        (O.Constructor "M_right", {ctor_type = r ; michelson_annotation = Some r_ann}); ]
+      in
+      return @@ O.T_sum (O.CMap.of_list sum)
     | I.T_operator type_operator ->
       let%bind type_operator = compile_type_operator type_operator in
       return @@ T_operator type_operator
@@ -157,12 +174,10 @@ and compile_type_operator : I.type_operator -> O.type_operator result =
     | TC_big_map (k,v) ->
       let%bind (k,v) = bind_map_pair compile_type_expression (k,v) in
       ok @@ O.TC_big_map (k,v)
-    | TC_michelson_or (l,r) ->
-      let%bind (l,r) = bind_map_pair compile_type_expression (l,r) in
-      ok @@ O.TC_michelson_or (l,r)
     | TC_arrow (i,o) ->
       let%bind (i,o) = bind_map_pair compile_type_expression (i,o) in
       ok @@ O.TC_arrow (i,o)
+    | TC_michelson_or _ -> fail @@ Errors.corner_case __LOC__
 
 let rec compile_expression : I.expression -> O.expression result =
   fun e ->
@@ -558,10 +573,12 @@ let rec uncompile_type_expression : O.type_expression -> I.type_expression resul
   let return te = ok @@ I.make_t te in
   match te.type_content with
     | O.T_sum sum -> 
+      (* This type sum could be a michelson_or as well, we could use is_michelson_or *)
       let sum = I.CMap.to_kv_list sum in
       let%bind sum = 
         bind_map_list (fun (k,v) ->
-          let%bind v = uncompile_type_expression v in
+          let {ctor_type;_} : O.ctor_content = v in
+          let%bind v = uncompile_type_expression ctor_type in
           ok @@ (k,v)
         ) sum
       in
@@ -609,9 +626,6 @@ and uncompile_type_operator : O.type_operator -> I.type_operator result =
     | TC_big_map (k,v) ->
       let%bind (k,v) = bind_map_pair uncompile_type_expression (k,v) in
       ok @@ I.TC_big_map (k,v)
-    | TC_michelson_or (l,r) ->
-      let%bind (l,r) = bind_map_pair uncompile_type_expression (l,r) in
-      ok @@ I.TC_michelson_or (l,r)
     | TC_arrow (i,o) ->
       let%bind (i,o) = bind_map_pair uncompile_type_expression (i,o) in
       ok @@ I.TC_arrow (i,o)
diff --git a/src/passes/5-self_ast_sugar/helpers.ml b/src/passes/5-self_ast_sugar/helpers.ml
index 856cb680a..4559e0429 100644
--- a/src/passes/5-self_ast_sugar/helpers.ml
+++ b/src/passes/5-self_ast_sugar/helpers.ml
@@ -2,6 +2,13 @@ open Ast_sugar
 open Trace
 open Stage_common.Helpers
 
+let bind_map_cmap f map = bind_cmap (
+  CMap.map 
+    (fun ({ctor_type;_} as ctor) -> 
+      let%bind ctor' = f ctor_type in
+      ok {ctor with ctor_type = ctor'}) 
+    map)
+
 type 'a folder = 'a -> expression -> 'a result
 let rec fold_expression : 'a folder -> 'a -> expression -> 'a result = fun f init e ->
   let self = fold_expression f in 
diff --git a/src/passes/6-sugar_to_core/sugar_to_core.ml b/src/passes/6-sugar_to_core/sugar_to_core.ml
index e13cdfda1..97e8ea2e2 100644
--- a/src/passes/6-sugar_to_core/sugar_to_core.ml
+++ b/src/passes/6-sugar_to_core/sugar_to_core.ml
@@ -10,8 +10,10 @@ let rec idle_type_expression : I.type_expression -> O.type_expression result =
       let sum = I.CMap.to_kv_list sum in
       let%bind sum = 
         bind_map_list (fun (k,v) ->
-          let%bind v = idle_type_expression v in
-          ok @@ (k,v)
+          let {ctor_type ; michelson_annotation} : I.ctor_content = v in
+          let%bind ctor_type = idle_type_expression ctor_type in
+          let v' : O.ctor_content = {ctor_type ; michelson_annotation} in
+          ok @@ (k,v')
         ) sum
       in
       return @@ O.T_sum (O.CMap.of_list sum)
@@ -62,9 +64,6 @@ and idle_type_operator : I.type_operator -> O.type_operator result =
     | TC_big_map (k,v) ->
       let%bind (k,v) = bind_map_pair idle_type_expression (k,v) in
       ok @@ O.TC_big_map (k,v)
-    | TC_michelson_or (l,r) ->
-      let%bind (l,r) = bind_map_pair idle_type_expression (l,r) in
-      ok @@ O.TC_michelson_or (l,r)
     | TC_arrow (i,o) ->
       let%bind (i,o) = bind_map_pair idle_type_expression (i,o) in
       ok @@ O.TC_arrow (i,o)
@@ -244,8 +243,10 @@ let rec uncompile_type_expression : O.type_expression -> I.type_expression resul
       let sum = I.CMap.to_kv_list sum in
       let%bind sum = 
         bind_map_list (fun (k,v) ->
-          let%bind v = uncompile_type_expression v in
-          ok @@ (k,v)
+          let {ctor_type;michelson_annotation} : O.ctor_content = v in
+          let%bind ctor_type = uncompile_type_expression ctor_type in
+          let v' : I.ctor_content = {ctor_type;michelson_annotation} in
+          ok @@ (k,v')
         ) sum
       in
       return @@ I.T_sum (O.CMap.of_list sum)
@@ -290,9 +291,6 @@ and uncompile_type_operator : O.type_operator -> I.type_operator result =
       let%bind (k,v) = bind_map_pair uncompile_type_expression (k,v) in
       ok @@ I.TC_big_map (k,v)
     | TC_map_or_big_map _ -> failwith "TC_map_or_big_map shouldn't be uncompiled"
-    | TC_michelson_or (l,r) ->
-      let%bind (l,r) = bind_map_pair uncompile_type_expression (l,r) in
-      ok @@ I.TC_michelson_or (l,r)
     | TC_arrow (i,o) ->
       let%bind (i,o) = bind_map_pair uncompile_type_expression (i,o) in
       ok @@ I.TC_arrow (i,o)
diff --git a/src/passes/7-self_ast_core/helpers.ml b/src/passes/7-self_ast_core/helpers.ml
index 8d669ddb6..b133faef4 100644
--- a/src/passes/7-self_ast_core/helpers.ml
+++ b/src/passes/7-self_ast_core/helpers.ml
@@ -2,6 +2,16 @@ open Ast_core
 open Trace
 open Stage_common.Helpers
 
+include Stage_common.PP
+include Stage_common.Types.Ast_generic_type(Ast_core_parameter)
+
+let bind_map_cmap f map = bind_cmap (
+  CMap.map 
+    (fun ({ctor_type;_} as ctor) -> 
+      let%bind ctor' = f ctor_type in
+      ok {ctor with ctor_type = ctor'}) 
+    map)
+
 type 'a folder = 'a -> expression -> 'a result
 let rec fold_expression : 'a folder -> 'a -> expression -> 'a result = fun f init e ->
   let self = fold_expression f in 
diff --git a/src/passes/7-self_ast_core/self_ast_core.ml b/src/passes/7-self_ast_core/self_ast_core.ml
new file mode 100644
index 000000000..56a41f46f
--- /dev/null
+++ b/src/passes/7-self_ast_core/self_ast_core.ml
@@ -0,0 +1,24 @@
+open Trace
+
+let all_expression_mapper = [
+]
+let all_type_expression_mapper = [
+]
+
+let all_exp = List.map (fun el -> Helpers.Expression el) all_expression_mapper
+let all_ty = List.map (fun el -> Helpers.Type_expression el) all_type_expression_mapper
+
+let all_program =
+  let all_p = List.map Helpers.map_program all_exp in
+  let all_p2 = List.map Helpers.map_program all_ty in
+  bind_chain (List.append all_p all_p2)
+
+let all_expression =
+  let all_p = List.map Helpers.map_expression all_expression_mapper in
+  bind_chain all_p
+
+let map_expression = Helpers.map_expression
+
+let fold_expression = Helpers.fold_expression
+
+let fold_map_expression = Helpers.fold_map_expression
diff --git a/src/passes/8-typer-new/PP.ml b/src/passes/8-typer-new/PP.ml
index 78520eb20..abecd4ef7 100644
--- a/src/passes/8-typer-new/PP.ml
+++ b/src/passes/8-typer-new/PP.ml
@@ -11,7 +11,6 @@ let type_constraint : _ -> type_constraint_simpl -> unit = fun ppf ->
       | Solver.Core.C_variant      -> failwith "variant"
       | Solver.Core.C_map          -> "map"
       | Solver.Core.C_big_map      -> "big_map"
-      | Solver.Core.C_michelson_or -> "michelson_or"
       | Solver.Core.C_list         -> "list"
       | Solver.Core.C_set          -> "set"
       | Solver.Core.C_unit         -> "unit"
diff --git a/src/passes/8-typer-new/solver.ml b/src/passes/8-typer-new/solver.ml
index d7bbd220e..ce2ba87d8 100644
--- a/src/passes/8-typer-new/solver.ml
+++ b/src/passes/8-typer-new/solver.ml
@@ -387,97 +387,93 @@ let compare_simple_c_constant = function
   | C_arrow -> (function
       (* N/A -> 1 *)
       | C_arrow -> 0
-      | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
+      | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_option -> (function
       | C_arrow -> 1
       | C_option -> 0
-      | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
+      | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_record -> (function
       | C_arrow | C_option  -> 1
       | C_record -> 0
-      | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
+      | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_variant -> (function
       | C_arrow | C_option  | C_record -> 1
       | C_variant -> 0
-      | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
+      | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_map -> (function
       | C_arrow | C_option  | C_record | C_variant -> 1
       | C_map -> 0
-      | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
+      | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_big_map -> (function
       | C_arrow | C_option  | C_record | C_variant | C_map -> 1
       | C_big_map -> 0
-      | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
-  | C_michelson_or -> (function
-      | C_arrow | C_option  | C_record | C_variant | C_map | C_big_map -> 1
-      | C_michelson_or -> 0
       | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_list -> (function
-      | C_arrow | C_option  | C_record | C_variant | C_map | C_big_map | C_michelson_or -> 1
+      | C_arrow | C_option  | C_record | C_variant | C_map | C_big_map -> 1
       | C_list -> 0
       | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_set -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list -> 1
       | C_set -> 0
       | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_unit -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set -> 1
       | C_unit -> 0
       | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_bool -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit -> 1
       | C_bool -> 0
       | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_string -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool -> 1
       | C_string -> 0
       | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_nat -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string -> 1
       | C_nat -> 0
       | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_mutez -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat -> 1
       | C_mutez -> 0
       | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_timestamp -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez -> 1
       | C_timestamp -> 0
       | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_int -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp -> 1
       | C_int -> 0
       | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_address -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int -> 1
       | C_address -> 0
       | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_bytes -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address -> 1
       | C_bytes -> 0
       | C_key_hash | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_key_hash -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes -> 1
       | C_key_hash -> 0
       | C_key | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_key -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash -> 1
       | C_key -> 0
       | C_signature | C_operation | C_contract | C_chain_id -> -1)
   | C_signature -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key -> 1
       | C_signature -> 0
       | C_operation | C_contract | C_chain_id -> -1)
   | C_operation -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature -> 1
       | C_operation -> 0
       | C_contract | C_chain_id -> -1)
   | C_contract -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation -> 1
       | C_contract -> 0
       | C_chain_id -> -1)
   | C_chain_id -> (function
-      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_michelson_or | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract -> 1
+      | C_arrow | C_option | C_record | C_variant | C_map | C_big_map | C_list | C_set | C_unit | C_bool | C_string | C_nat | C_mutez | C_timestamp | C_int | C_address | C_bytes | C_key_hash | C_key | C_signature | C_operation | C_contract -> 1
       | C_chain_id -> 0
       (* N/A -> -1 *)
     )
@@ -493,7 +489,6 @@ let debug_pp_constant : _ -> constant_tag -> unit = fun ppf c_tag ->
       | Core.C_variant   -> failwith "variant"
       | Core.C_map       -> "map"
       | Core.C_big_map   -> "big_map"
-      | Core.C_michelson_or -> "michelson_or"
       | Core.C_list      -> "list"
       | Core.C_set       -> "set"
       | Core.C_unit      -> "unit"
diff --git a/src/passes/8-typer-new/typer.ml b/src/passes/8-typer-new/typer.ml
index b8f875e7e..1d602f458 100644
--- a/src/passes/8-typer-new/typer.ml
+++ b/src/passes/8-typer-new/typer.ml
@@ -138,8 +138,9 @@ and evaluate_type (e:environment) (t:I.type_expression) : O.type_expression resu
   | T_sum m ->
     let aux k v prev =
       let%bind prev' = prev in
-      let%bind v' = evaluate_type e v in
-      ok @@ O.CMap.add (convert_constructor' k) v' prev'
+      let {ctor_type ; michelson_annotation} : I.ctor_content = v in
+      let%bind ctor_type = evaluate_type e ctor_type in
+      ok @@ O.CMap.add (convert_constructor' k) ({ctor_type ; michelson_annotation}:O.ctor_content) prev'
     in
     let%bind m = I.CMap.fold aux m (ok O.CMap.empty) in
     return (T_sum m)
@@ -181,10 +182,6 @@ and evaluate_type (e:environment) (t:I.type_expression) : O.type_expression resu
             let%bind k = evaluate_type e k in
             let%bind v = evaluate_type e v in
             ok @@ O.TC_map_or_big_map {k;v}
-        | TC_michelson_or (l,r) ->
-            let%bind l = evaluate_type e l in 
-            let%bind r = evaluate_type e r in 
-            ok @@ O.TC_michelson_or {l;r} 
         | TC_contract c ->
             let%bind c = evaluate_type e c in
             ok @@ O.TC_contract c
diff --git a/src/passes/8-typer-new/untyper.ml b/src/passes/8-typer-new/untyper.ml
index 0f0803f8e..0d3c56162 100644
--- a/src/passes/8-typer-new/untyper.ml
+++ b/src/passes/8-typer-new/untyper.ml
@@ -149,9 +149,10 @@ let rec untype_type_expression (t:O.type_expression) : (I.type_expression) resul
   (* TODO: or should we use t.core if present? *)
   let%bind t = match t.type_content with
   | O.T_sum x ->
-    let aux k v acc =
+    let aux k ({ctor_type ; michelson_annotation} : O.ctor_content) acc =
       let%bind acc = acc in
-      let%bind v' = untype_type_expression v in
+      let%bind ctor_type = untype_type_expression ctor_type in
+      let v' : I.ctor_content = {ctor_type ; michelson_annotation} in 
       ok @@ I.CMap.add (unconvert_constructor' k) v' acc in
     let%bind x' = O.CMap.fold aux x (ok I.CMap.empty) in
     ok @@ I.T_sum x'
@@ -192,10 +193,6 @@ let rec untype_type_expression (t:O.type_expression) : (I.type_expression) resul
          let%bind k = untype_type_expression k in
          let%bind v = untype_type_expression v in
          ok @@ I.TC_map_or_big_map (k,v)
-      | O.TC_michelson_or {l;r} ->     
-         let%bind l = untype_type_expression l in
-         let%bind r = untype_type_expression r in
-         ok @@ I.TC_michelson_or (l,r)
       | O.TC_arrow { type1=arg ; type2=ret } ->
          let%bind arg' = untype_type_expression arg in
          let%bind ret' = untype_type_expression ret in
diff --git a/src/passes/8-typer-new/wrap.ml b/src/passes/8-typer-new/wrap.ml
index 55e7c3257..5355e7bc8 100644
--- a/src/passes/8-typer-new/wrap.ml
+++ b/src/passes/8-typer-new/wrap.ml
@@ -34,7 +34,8 @@ let rec type_expression_to_type_value : T.type_expression -> O.type_value = fun
   match te.type_content with
   | T_sum kvmap ->
      let () = failwith "fixme: don't use to_list, it drops the variant keys, rows have a differnt kind than argument lists for now!" in
-     P_constant (C_variant, T.CMap.to_list @@ T.CMap.map type_expression_to_type_value kvmap)
+     let tlist = List.map (fun ({ctor_type;_}:T.ctor_content) -> ctor_type) (T.CMap.to_list kvmap) in
+     P_constant (C_variant, List.map type_expression_to_type_value tlist)
   | T_record kvmap ->
      let () = failwith "fixme: don't use to_list, it drops the record keys, rows have a differnt kind than argument lists for now!" in
      P_constant (C_record, T.LMap.to_list @@ T.LMap.map type_expression_to_type_value kvmap)
@@ -69,7 +70,6 @@ let rec type_expression_to_type_value : T.type_expression -> O.type_value = fun
                                 | TC_map { k ; v }           -> (C_map, [k;v])
                                 | TC_big_map { k ; v }       -> (C_big_map, [k;v])
                                 | TC_map_or_big_map { k ; v } -> (C_map, [k;v])
-                                | TC_michelson_or { l; r } -> (C_michelson_or, [l;r])
                                 | TC_arrow { type1 ; type2 } -> (C_arrow, [ type1 ; type2 ])
                                 | TC_list l                  -> (C_list, [l])
                                 | TC_contract c              -> (C_contract, [c])
@@ -81,7 +81,8 @@ let rec type_expression_to_type_value_copypasted : I.type_expression -> O.type_v
   match te.type_content with
   | T_sum kvmap ->
      let () = failwith "fixme: don't use to_list, it drops the variant keys, rows have a differnt kind than argument lists for now!" in
-     P_constant (C_variant, I.CMap.to_list @@ I.CMap.map type_expression_to_type_value_copypasted kvmap)
+     let tlist = List.map (fun ({ctor_type;_}:I.ctor_content) -> ctor_type) (I.CMap.to_list kvmap) in
+     P_constant (C_variant, List.map type_expression_to_type_value_copypasted tlist)
   | T_record kvmap ->
      let () = failwith "fixme: don't use to_list, it drops the record keys, rows have a differnt kind than argument lists for now!" in
      P_constant (C_record, I.LMap.to_list @@ I.LMap.map type_expression_to_type_value_copypasted kvmap)
@@ -104,7 +105,6 @@ let rec type_expression_to_type_value_copypasted : I.type_expression -> O.type_v
                                 | TC_map  ( k , v )      -> (C_map    , [k;v])
                                 | TC_big_map  ( k , v )  -> (C_big_map, [k;v])
                                 | TC_map_or_big_map ( k , v) -> (C_map, [k;v])
-                                | TC_michelson_or ( k , v ) -> (C_michelson_or, [k;v])
                                 | TC_contract c          -> (C_contract, [c])
                                 | TC_arrow ( arg , ret ) -> (C_arrow, [ arg ; ret ])
                           )
diff --git a/src/passes/8-typer-old/typer.ml b/src/passes/8-typer-old/typer.ml
index 976459200..d1ab5fbb2 100644
--- a/src/passes/8-typer-old/typer.ml
+++ b/src/passes/8-typer-old/typer.ml
@@ -596,15 +596,16 @@ and evaluate_type (e:environment) (t:I.type_expression) : O.type_expression resu
       let%bind type2 = evaluate_type e type2 in
       return (T_arrow {type1;type2})
   | T_sum m ->
-      let aux k v prev =
+      let aux k ({ctor_type;michelson_annotation} : I.ctor_content) prev =
         let%bind prev' = prev in
-        let%bind v' = evaluate_type e v in
+        let%bind ctor_type = evaluate_type e ctor_type in
         let%bind () = match Environment.get_constructor k e with
           | Some _ ->
             if I.CMap.mem (Constructor "M_left") m || I.CMap.mem (Constructor "M_right") m then
               ok ()
             else fail (redundant_constructor e k)
           | None -> ok () in
+        let v' : O.ctor_content = {ctor_type;michelson_annotation} in
         ok @@ O.CMap.add (convert_constructor' k) v' prev'
       in
       let%bind m = I.CMap.fold aux m (ok O.CMap.empty) in
@@ -647,10 +648,6 @@ and evaluate_type (e:environment) (t:I.type_expression) : O.type_expression resu
             let%bind k = evaluate_type e k in 
             let%bind v = evaluate_type e v in 
             ok @@ O.TC_map_or_big_map {k;v}
-        | TC_michelson_or (l,r) ->
-            let%bind l = evaluate_type e l in 
-            let%bind r = evaluate_type e r in 
-            ok @@ O.TC_michelson_or {l;r}
         | TC_arrow ( arg , ret ) ->
             let%bind arg' = evaluate_type e arg in
             let%bind ret' = evaluate_type e ret in
@@ -744,8 +741,8 @@ and type_expression' : environment -> ?tv_opt:O.type_expression -> I.expression
     let%bind expr' = type_expression' e element in
     ( match t.type_content with
       | T_sum c ->
-        let ct = O.CMap.find (O.Constructor s) c in
-        let%bind _assert = O.assert_type_expression_eq (expr'.type_expression, ct) in
+        let {ctor_type ; _} : O.ctor_content = O.CMap.find (O.Constructor s) c in
+        let%bind _assert = O.assert_type_expression_eq (expr'.type_expression, ctor_type) in
         return (E_constructor {constructor = Constructor s; element=expr'}) t
       | _ -> simple_fail "ll" 
     )
diff --git a/src/passes/9-self_ast_typed/contract_passes.ml b/src/passes/9-self_ast_typed/contract_passes.ml
index d3877bd39..a98d466e8 100644
--- a/src/passes/9-self_ast_typed/contract_passes.ml
+++ b/src/passes/9-self_ast_typed/contract_passes.ml
@@ -62,8 +62,10 @@ let self_typing : contract_pass_data -> expression -> (bool * contract_pass_data
       | E_literal (Literal_string ep) -> check_entrypoint_annotation_format ep entrypoint_exp
       | _ -> fail @@ Errors.entrypoint_annotation_not_literal entrypoint_exp.location in
     let%bind entrypoint_t = match dat.contract_type.parameter.type_content with
-      | T_sum cmap -> trace_option (Errors.unmatched_entrypoint entrypoint_exp.location)
-                      @@ CMap.find_opt (Constructor entrypoint) cmap
+      | T_sum cmap ->
+        let%bind {ctor_type;_} = trace_option (Errors.unmatched_entrypoint entrypoint_exp.location) @@
+          CMap.find_opt (Constructor entrypoint) cmap in
+        ok ctor_type
       | t -> ok {dat.contract_type.parameter with type_content = t} in
     let%bind () =
       trace_strong (bad_self_err ()) @@
diff --git a/src/passes/9-self_ast_typed/no_nested_big_map.ml b/src/passes/9-self_ast_typed/no_nested_big_map.ml
index f90a9b203..8f8f9d51e 100644
--- a/src/passes/9-self_ast_typed/no_nested_big_map.ml
+++ b/src/passes/9-self_ast_typed/no_nested_big_map.ml
@@ -39,12 +39,8 @@ let rec check_no_nested_bigmap is_in_bigmap e =
     let%bind _ = check_no_nested_bigmap false type1 in
     let%bind _ = check_no_nested_bigmap false type2 in
     ok ()
-  | T_operator (TC_michelson_or {l; r}) -> 
-    let%bind _ = check_no_nested_bigmap false l in
-    let%bind _ = check_no_nested_bigmap false r in
-    ok ()
   | T_sum s -> 
-    let es = CMap.to_list s in
+    let es = List.map (fun {ctor_type;_} -> ctor_type) (CMap.to_list s) in
     let%bind _ = bind_map_list (fun l -> check_no_nested_bigmap is_in_bigmap l) es in
     ok ()
   | T_record elm -> 
diff --git a/src/passes/operators/operators.ml b/src/passes/operators/operators.ml
index 1cf4407ae..0400a3606 100644
--- a/src/passes/operators/operators.ml
+++ b/src/passes/operators/operators.ml
@@ -59,7 +59,7 @@ module Concrete_to_imperative = struct
     | "set"          -> ok @@ TC_set unit_expr
     | "map"          -> ok @@ TC_map (unit_expr,unit_expr)
     | "big_map"      -> ok @@ TC_big_map (unit_expr,unit_expr)
-    | "michelson_or" -> ok @@ TC_michelson_or (unit_expr,unit_expr)
+    | "michelson_or" -> ok @@ TC_michelson_or (unit_expr,"",unit_expr,"")
     | "contract"     -> ok @@ TC_contract unit_expr
     | _              -> simple_fail @@ "Not a built-in type (" ^ s ^ ")."
 
diff --git a/src/stages/1-ast_imperative/PP.ml b/src/stages/1-ast_imperative/PP.ml
index 4d735677b..da65ae284 100644
--- a/src/stages/1-ast_imperative/PP.ml
+++ b/src/stages/1-ast_imperative/PP.ml
@@ -5,6 +5,14 @@ open PP_helpers
 
 include Stage_common.PP
 
+let cmap_sep value sep ppf m =
+  let lst = CMap.to_kv_list m in
+  let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) lst in
+  let new_pp ppf (k, v) = fprintf ppf "@[<h>%a -> %a@]" constructor k value v in
+  fprintf ppf "%a" (list_sep new_pp sep) lst
+
+let cmap_sep_d x = cmap_sep x (tag " ,@ ")
+
 let expression_variable ppf (ev : expression_variable) : unit =
   fprintf ppf "%a" Var.pp ev
 
@@ -39,7 +47,7 @@ and type_operator :
     | TC_set te -> Format.asprintf "set(%a)" f te
     | TC_map (k, v) -> Format.asprintf "Map (%a,%a)" f k f v
     | TC_big_map (k, v) -> Format.asprintf "Big Map (%a,%a)" f k f v
-    | TC_michelson_or (l, r) -> Format.asprintf "Michelson_or (%a,%a)" f l f r
+    | TC_michelson_or (l,_, r,_) -> Format.asprintf "Michelson_or (%a,%a)" f l f r
     | TC_arrow (k, v) -> Format.asprintf "arrow (%a,%a)" f k f v
     | TC_contract te  -> Format.asprintf "Contract (%a)" f te
   in
diff --git a/src/stages/1-ast_imperative/combinators.ml b/src/stages/1-ast_imperative/combinators.ml
index c8b8be570..e8db1428f 100644
--- a/src/stages/1-ast_imperative/combinators.ml
+++ b/src/stages/1-ast_imperative/combinators.ml
@@ -59,9 +59,9 @@ let t_sum ?loc m : type_expression =
 let t_function ?loc type1 type2  : type_expression = make_t ?loc @@ T_arrow {type1; type2}
 let t_map ?loc key value         : type_expression = make_t ?loc @@ T_operator (TC_map (key, value))
 let t_big_map ?loc key value     : type_expression = make_t ?loc @@ T_operator (TC_big_map (key , value))
-let t_michelson_or ?loc l r      : type_expression = make_t ?loc @@ T_operator (TC_michelson_or (l , r))
 let t_set ?loc key               : type_expression = make_t ?loc @@ T_operator (TC_set key)
 let t_contract ?loc contract     : type_expression = make_t ?loc @@ T_operator (TC_contract contract)
+let t_michelson_or ?loc l l_ann r r_ann : type_expression = make_t ?loc @@ T_operator (TC_michelson_or (l, l_ann, r, r_ann))
 
 (* TODO find a better way than using list*)
 let t_operator ?loc op lst: type_expression result =
@@ -71,7 +71,7 @@ let t_operator ?loc op lst: type_expression result =
   | TC_option _      , [t] -> ok @@ t_option ?loc t
   | TC_map (_,_)     , [kt;vt] -> ok @@ t_map ?loc kt vt
   | TC_big_map (_,_) , [kt;vt] -> ok @@ t_big_map ?loc kt vt
-  | TC_michelson_or (_,_) , [l;r] -> ok @@ t_michelson_or ?loc l r
+  | TC_michelson_or (_,l_ann,_,r_ann) , [l;r] -> ok @@ t_michelson_or ?loc l l_ann r r_ann
   | TC_contract _    , [t] -> ok @@ t_contract t
   | _ , _ -> fail @@ bad_type_operator op
 
diff --git a/src/stages/1-ast_imperative/combinators.mli b/src/stages/1-ast_imperative/combinators.mli
index 1d582184f..39f0fb3f5 100644
--- a/src/stages/1-ast_imperative/combinators.mli
+++ b/src/stages/1-ast_imperative/combinators.mli
@@ -42,6 +42,10 @@ val ez_t_sum : ?loc:Location.t -> ( string * type_expression ) list -> type_expr
 
 val t_function : ?loc:Location.t -> type_expression -> type_expression -> type_expression
 val t_map      : ?loc:Location.t -> type_expression -> type_expression -> type_expression
+val t_michelson_or : ?loc:Location.t ->
+type_expression ->
+michelson_prct_annotation ->
+type_expression -> michelson_prct_annotation -> type_expression
 
 val t_operator : ?loc:Location.t -> type_operator -> type_expression list -> type_expression result
 val t_set      : ?loc:Location.t -> type_expression -> type_expression
diff --git a/src/stages/1-ast_imperative/types.ml b/src/stages/1-ast_imperative/types.ml
index f334a370e..8cdc8c6eb 100644
--- a/src/stages/1-ast_imperative/types.ml
+++ b/src/stages/1-ast_imperative/types.ml
@@ -15,6 +15,8 @@ type type_content =
 
 and arrow = {type1: type_expression; type2: type_expression}
 
+and michelson_prct_annotation = string
+
 and type_operator =
   | TC_contract of type_expression
   | TC_option of type_expression
@@ -22,7 +24,7 @@ and type_operator =
   | TC_set of type_expression
   | TC_map of type_expression * type_expression
   | TC_big_map of type_expression * type_expression
-  | TC_michelson_or of type_expression * type_expression
+  | TC_michelson_or of type_expression * michelson_prct_annotation * type_expression * michelson_prct_annotation
   | TC_arrow of type_expression * type_expression
 
 and type_expression = {type_content: type_content; location: Location.t}
diff --git a/src/stages/2-ast_sugar/PP.ml b/src/stages/2-ast_sugar/PP.ml
index 419cbb724..4375d1db3 100644
--- a/src/stages/2-ast_sugar/PP.ml
+++ b/src/stages/2-ast_sugar/PP.ml
@@ -4,6 +4,15 @@ open Format
 open PP_helpers
 
 include Stage_common.PP
+include Stage_common.PP.Ast_PP_type(Ast_sugar_parameter)
+
+let cmap_sep value sep ppf m =
+  let lst = CMap.to_kv_list m in
+  let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) lst in
+  let new_pp ppf (k, {ctor_type;_}) = fprintf ppf "@[<h>%a -> %a@]" constructor k value ctor_type in
+  fprintf ppf "%a" (list_sep new_pp sep) lst
+
+let cmap_sep_d x = cmap_sep x (tag " ,@ ")
 
 let expression_variable ppf (ev : expression_variable) : unit =
   fprintf ppf "%a" Var.pp ev
@@ -15,7 +24,7 @@ let rec type_expression' :
     -> unit =
   fun f ppf te ->
   match te.type_content with
-  | T_sum m -> fprintf ppf "sum[%a]" (cmap_sep_d f) m
+  | T_sum m -> fprintf ppf "@[<hv 4>sum[%a]@]" (cmap_sep_d f) m
   | T_record m -> fprintf ppf "{%a}" (record_sep f (const ";")) m
   | T_tuple  t -> fprintf ppf "(%a)" (list_sep_d f) t
   | T_arrow  a -> fprintf ppf "%a -> %a" f a.type1 f a.type2
@@ -35,7 +44,6 @@ and type_operator : (formatter -> type_expression -> unit) -> formatter -> type_
     | TC_set te -> Format.asprintf "set(%a)" f te
     | TC_map (k, v) -> Format.asprintf "Map (%a,%a)" f k f v
     | TC_big_map (k, v) -> Format.asprintf "Big Map (%a,%a)" f k f v
-    | TC_michelson_or (l, r) -> Format.asprintf "Michelson_or (%a,%a)" f l f r
     | TC_arrow (k, v) -> Format.asprintf "arrow (%a,%a)" f k f v
     | TC_contract te  -> Format.asprintf "Contract (%a)" f te
   in
diff --git a/src/stages/2-ast_sugar/combinators.ml b/src/stages/2-ast_sugar/combinators.ml
index dad7106d3..60c2758da 100644
--- a/src/stages/2-ast_sugar/combinators.ml
+++ b/src/stages/2-ast_sugar/combinators.ml
@@ -54,7 +54,7 @@ let t_record ?loc m  : type_expression =
 let t_pair ?loc (a , b) : type_expression = t_record_ez ?loc [("0",a) ; ("1",b)]
 let t_tuple ?loc lst    : type_expression = t_record_ez ?loc (tuple_to_record lst)
 
-let ez_t_sum ?loc (lst:(string * type_expression) list) : type_expression =
+let ez_t_sum ?loc (lst:((string * ctor_content) list)) : type_expression =
   let aux prev (k, v) = CMap.add (Constructor k) v prev in
   let map = List.fold_left aux CMap.empty lst in
   make_t ?loc @@ T_sum map
diff --git a/src/stages/2-ast_sugar/combinators.mli b/src/stages/2-ast_sugar/combinators.mli
index ca4605e4e..e83a307ef 100644
--- a/src/stages/2-ast_sugar/combinators.mli
+++ b/src/stages/2-ast_sugar/combinators.mli
@@ -37,8 +37,8 @@ val t_tuple  : ?loc:Location.t -> type_expression list -> type_expression
 val t_record    : ?loc:Location.t -> type_expression Map.String.t -> type_expression
 val t_record_ez : ?loc:Location.t -> (string * type_expression) list -> type_expression
 
-val t_sum    : ?loc:Location.t -> type_expression Map.String.t -> type_expression
-val ez_t_sum : ?loc:Location.t -> ( string * type_expression ) list -> type_expression
+val t_sum    : ?loc:Location.t -> ctor_content Map.String.t -> type_expression
+val ez_t_sum : ?loc:Location.t -> ( string * ctor_content ) list -> type_expression
 
 val t_function : ?loc:Location.t -> type_expression -> type_expression -> type_expression
 val t_map      : ?loc:Location.t -> type_expression -> type_expression -> type_expression
diff --git a/src/stages/2-ast_sugar/types.ml b/src/stages/2-ast_sugar/types.ml
index 47c11d68f..4e673d1b5 100644
--- a/src/stages/2-ast_sugar/types.ml
+++ b/src/stages/2-ast_sugar/types.ml
@@ -4,8 +4,12 @@ module Location = Simple_utils.Location
 
 include Stage_common.Types
 
+module Ast_sugar_parameter = struct
+  type type_meta = unit
+end
+
 type type_content =
-  | T_sum of type_expression constructor_map
+  | T_sum of ctor_content constructor_map
   | T_record of type_expression label_map
   | T_tuple  of type_expression list
   | T_arrow of arrow
@@ -15,13 +19,14 @@ type type_content =
 
 and arrow = {type1: type_expression; type2: type_expression}
 
+and ctor_content = {ctor_type : type_expression ; michelson_annotation : string option}
+
 and type_operator =
   | TC_contract of type_expression
   | TC_option of type_expression
   | TC_list of type_expression
   | TC_set of type_expression
   | TC_map of type_expression * type_expression
-  | TC_michelson_or of type_expression * type_expression
   | TC_big_map of type_expression * type_expression
   | TC_arrow of type_expression * type_expression
 
diff --git a/src/stages/3-ast_core/combinators.ml b/src/stages/3-ast_core/combinators.ml
index 2308cb5b3..aff739d8a 100644
--- a/src/stages/3-ast_core/combinators.ml
+++ b/src/stages/3-ast_core/combinators.ml
@@ -54,7 +54,7 @@ let t_record ?loc m  : type_expression =
 let t_pair ?loc (a , b) : type_expression = t_record_ez ?loc [("0",a) ; ("1",b)]
 let t_tuple ?loc lst    : type_expression = t_record_ez ?loc (tuple_to_record lst)
 
-let ez_t_sum ?loc (lst:(string * type_expression) list) : type_expression =
+let ez_t_sum ?loc (lst:(string * ctor_content) list) : type_expression =
   let aux prev (k, v) = CMap.add (Constructor k) v prev in
   let map = List.fold_left aux CMap.empty lst in
   make_t ?loc @@ T_sum map
diff --git a/src/stages/3-ast_core/combinators.mli b/src/stages/3-ast_core/combinators.mli
index 7320af576..631c36110 100644
--- a/src/stages/3-ast_core/combinators.mli
+++ b/src/stages/3-ast_core/combinators.mli
@@ -37,8 +37,8 @@ val t_tuple  : ?loc:Location.t -> type_expression list -> type_expression
 val t_record    : ?loc:Location.t -> type_expression Map.String.t -> type_expression
 val t_record_ez : ?loc:Location.t -> (string * type_expression) list -> type_expression
 
-val t_sum    : ?loc:Location.t -> type_expression Map.String.t -> type_expression
-val ez_t_sum : ?loc:Location.t -> ( string * type_expression ) list -> type_expression
+val t_sum    : ?loc:Location.t -> Types.ctor_content Map.String.t -> type_expression
+val ez_t_sum : ?loc:Location.t -> ( string * Types.ctor_content ) list -> type_expression
 
 val t_function : ?loc:Location.t -> type_expression -> type_expression -> type_expression
 val t_map      : ?loc:Location.t -> type_expression -> type_expression -> type_expression
diff --git a/src/stages/3-ast_core/types.ml b/src/stages/3-ast_core/types.ml
index 6c9637ac4..e925c5f3b 100644
--- a/src/stages/3-ast_core/types.ml
+++ b/src/stages/3-ast_core/types.ml
@@ -8,8 +8,6 @@ end
 
 include Stage_common.Types
 
-(*include Ast_generic_type(Ast_core_parameter)
-*)
 include Ast_generic_type (Ast_core_parameter)
 
 type inline = bool 
diff --git a/src/stages/4-ast_typed/PP.ml b/src/stages/4-ast_typed/PP.ml
index a5cf4c7f1..4b93422e3 100644
--- a/src/stages/4-ast_typed/PP.ml
+++ b/src/stages/4-ast_typed/PP.ml
@@ -15,8 +15,7 @@ let label ppf (l:label) : unit =
   let Label l = l in fprintf ppf "%s" l
 
 let cmap_sep value sep ppf m =
-  let lst = CMap.to_kv_list m in
-  let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) lst in
+  let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) m in
   let new_pp ppf (k, v) = fprintf ppf "@[<h>%a -> %a@]" constructor k value v in
   fprintf ppf "%a" (list_sep new_pp sep) lst
 
@@ -210,7 +209,7 @@ let rec type_expression' :
           -> unit =
   fun f ppf te ->
   match te.type_content with
-  | T_sum m -> fprintf ppf "@[<hv 4>sum[%a]@]" (cmap_sep_d f) m
+  | T_sum m -> fprintf ppf "@[<hv 4>sum[%a]@]" (cmap_sep_d f) (List.map (fun (c,{ctor_type;_}) -> (c,ctor_type)) (CMap.to_kv_list m))
   | T_record m -> fprintf ppf "%a" (tuple_or_record_sep_type f) m
   | T_arrow a -> fprintf ppf "%a -> %a" f a.type1 f a.type2
   | T_variable tv -> type_variable ppf tv
@@ -234,7 +233,6 @@ and type_operator :
     | TC_map {k; v} -> Format.asprintf "Map (%a,%a)" f k f v
     | TC_big_map {k; v} -> Format.asprintf "Big Map (%a,%a)" f k f v
     | TC_map_or_big_map {k; v} -> Format.asprintf "Map Or Big Map (%a,%a)" f k f v
-    | TC_michelson_or {l; r} -> Format.asprintf "michelson_or (%a,%a)" f l f r
     | TC_arrow {type1; type2} -> Format.asprintf "arrow (%a,%a)" f type1 f type2
     | TC_contract te  -> Format.asprintf "Contract (%a)" f te
   in
diff --git a/src/stages/4-ast_typed/combinators.ml b/src/stages/4-ast_typed/combinators.ml
index 6bfac897f..43613c100 100644
--- a/src/stages/4-ast_typed/combinators.ml
+++ b/src/stages/4-ast_typed/combinators.ml
@@ -67,7 +67,7 @@ let t_big_map ?loc k v ?s () = make_t ?loc (T_operator (TC_big_map { k ; v })) s
 let t_map_or_big_map ?loc k v ?s () = make_t ?loc (T_operator (TC_map_or_big_map { k ; v })) s
 
 let t_sum m ?loc ?s () : type_expression = make_t ?loc (T_sum m) s
-let make_t_ez_sum ?loc (lst:(constructor' * type_expression) list) : type_expression =
+let make_t_ez_sum ?loc (lst:(constructor' * ctor_content) list) : type_expression =
   let aux prev (k, v) = CMap.add k v prev in
   let map = List.fold_left aux CMap.empty lst in
   make_t ?loc (T_sum map) None
@@ -180,7 +180,7 @@ let get_t_function_full (t:type_expression) : (type_expression * type_expression
   let (input,output) = aux 0 t in
   ok @@ (t_record (LMap.of_list input) (),output) 
 
-let get_t_sum (t:type_expression) : type_expression constructor_map result = match t.type_content with
+let get_t_sum (t:type_expression) : ctor_content constructor_map result = match t.type_content with
   | T_sum m -> ok m
   | _ -> fail @@ Errors.not_a_x_type "sum" t ()
 
diff --git a/src/stages/4-ast_typed/combinators.mli b/src/stages/4-ast_typed/combinators.mli
index ffcad19f8..0b9315088 100644
--- a/src/stages/4-ast_typed/combinators.mli
+++ b/src/stages/4-ast_typed/combinators.mli
@@ -32,8 +32,8 @@ val ez_t_record : ( label * type_expression ) list -> ?loc:Location.t -> ?s:S.ty
 val t_map : ?loc:Location.t -> type_expression -> type_expression -> ?s:S.type_expression -> unit -> type_expression
 val t_big_map : ?loc:Location.t -> type_expression -> type_expression -> ?s:S.type_expression -> unit -> type_expression
 val t_map_or_big_map : ?loc:Location.t -> type_expression -> type_expression ->  ?s:S.type_expression -> unit -> type_expression
-val t_sum : type_expression constructor_map -> ?loc:Location.t -> ?s:S.type_expression -> unit -> type_expression
-val make_t_ez_sum : ?loc:Location.t -> ( constructor' * type_expression ) list -> type_expression
+val t_sum : Types.te_cmap -> ?loc:Location.t -> ?s:S.type_expression -> unit -> type_expression
+val make_t_ez_sum : ?loc:Location.t -> ( constructor' * ctor_content ) list -> type_expression
 val t_function : type_expression -> type_expression -> ?loc:Location.t -> ?s:S.type_expression -> unit -> type_expression
 val t_shallow_closure : type_expression -> type_expression -> ?loc:Location.t -> ?s:S.type_expression -> unit -> type_expression
 val get_type_expression : expression -> type_expression
@@ -64,7 +64,7 @@ val get_t_tuple : type_expression -> type_expression list result
 val get_t_pair : type_expression -> ( type_expression * type_expression ) result
 val get_t_function : type_expression -> ( type_expression * type_expression ) result
 val get_t_function_full : type_expression -> ( type_expression * type_expression ) result
-val get_t_sum : type_expression -> type_expression constructor_map result
+val get_t_sum : type_expression -> ctor_content constructor_map result
 val get_t_record : type_expression -> type_expression label_map result
 val get_t_map : type_expression -> ( type_expression * type_expression ) result
 val get_t_big_map : type_expression -> ( type_expression * type_expression ) result
diff --git a/src/stages/4-ast_typed/combinators_environment.ml b/src/stages/4-ast_typed/combinators_environment.ml
index 5d9ecddb6..5fcb358fa 100644
--- a/src/stages/4-ast_typed/combinators_environment.ml
+++ b/src/stages/4-ast_typed/combinators_environment.ml
@@ -21,5 +21,5 @@ open Environment
 
 let env_sum_type ?(env = full_empty)
     ?(type_name = Var.of_name "a_sum_type")
-    (lst : (constructor' * type_expression) list) =
+    (lst : (constructor' * ctor_content) list) =
   add_type type_name (make_t_ez_sum lst) env
diff --git a/src/stages/4-ast_typed/combinators_environment.mli b/src/stages/4-ast_typed/combinators_environment.mli
index 830ac7ee2..783b1d6a6 100644
--- a/src/stages/4-ast_typed/combinators_environment.mli
+++ b/src/stages/4-ast_typed/combinators_environment.mli
@@ -16,4 +16,4 @@ val e_a_empty_record : expression label_map -> expression
 val ez_e_a_empty_record : ( label * expression ) list -> expression
 val e_a_empty_lambda : lambda -> type_expression -> type_expression -> expression
 
-val env_sum_type : ?env:full_environment -> ?type_name:type_variable -> (constructor' * type_expression) list ->  full_environment
+val env_sum_type : ?env:full_environment -> ?type_name:type_variable -> (constructor' * ctor_content) list ->  full_environment
diff --git a/src/stages/4-ast_typed/environment.ml b/src/stages/4-ast_typed/environment.ml
index 2f83a978b..d1bc6dc73 100644
--- a/src/stages/4-ast_typed/environment.ml
+++ b/src/stages/4-ast_typed/environment.ml
@@ -51,7 +51,7 @@ let get_constructor : Ast_core.constructor' -> t -> (type_expression * type_expr
       match type_.type_content with
       | T_sum m ->
         (match CMap.find_opt (convert_constructor' k) m with
-           Some km -> Some (km , type_)
+           Some {ctor_type ; _} -> Some (ctor_type , type_)
          | None -> None)
       | _ -> None
     in
diff --git a/src/stages/4-ast_typed/helpers.ml b/src/stages/4-ast_typed/helpers.ml
index c7dff6989..67f7cd108 100644
--- a/src/stages/4-ast_typed/helpers.ml
+++ b/src/stages/4-ast_typed/helpers.ml
@@ -9,7 +9,6 @@ let map_type_operator f = function
   | TC_map {k ; v} -> TC_map { k = f k ; v = f v }
   | TC_big_map {k ; v}-> TC_big_map { k = f k ; v = f v }
   | TC_map_or_big_map { k ; v }-> TC_map_or_big_map { k = f k ; v = f v }
-  | TC_michelson_or { l ; r } -> TC_michelson_or { l = f l ; r = f r }
   | TC_arrow {type1 ; type2} -> TC_arrow { type1 = f type1 ; type2 = f type2 }
 
 let bind_map_type_operator f = function
@@ -20,7 +19,6 @@ let bind_map_type_operator f = function
   | TC_map {k ; v} -> let%bind k = f k in let%bind v = f v in ok @@ TC_map {k ; v}
   | TC_big_map {k ; v} -> let%bind k = f k in let%bind v = f v in ok @@ TC_big_map {k ; v}
   | TC_map_or_big_map {k ; v} -> let%bind k = f k in let%bind v = f v in ok @@ TC_map_or_big_map {k ; v}
-  | TC_michelson_or {l ; r}-> let%bind l = f l in let%bind r = f r in ok @@ TC_michelson_or {l ; r}
   | TC_arrow {type1 ; type2}-> let%bind type1 = f type1 in let%bind type2 = f type2 in ok @@ TC_arrow {type1 ; type2}
 
 let type_operator_name = function
@@ -31,7 +29,6 @@ let type_operator_name = function
   | TC_map      _ -> "TC_map"
   | TC_big_map  _ -> "TC_big_map"
   | TC_map_or_big_map _ -> "TC_map_or_big_map"
-  | TC_michelson_or   _ -> "TC_michelson_or"
   | TC_arrow    _ -> "TC_arrow"
 
 let type_expression'_of_string = function
@@ -71,7 +68,6 @@ let string_of_type_operator = function
   | TC_map            { k ; v }         -> "TC_map"      , [k ; v]
   | TC_big_map        { k ; v }         -> "TC_big_map"  , [k ; v]
   | TC_map_or_big_map { k ; v }         -> "TC_map_or_big_map"  , [k ; v]
-  | TC_michelson_or   { l ; r }         -> "TC_michelson_or"    , [l ; r]
   | TC_arrow          { type1 ; type2 } -> "TC_arrow"    , [type1 ; type2]
 
 let string_of_type_constant = function
diff --git a/src/stages/4-ast_typed/misc.ml b/src/stages/4-ast_typed/misc.ml
index 152c462dc..423220a13 100644
--- a/src/stages/4-ast_typed/misc.ml
+++ b/src/stages/4-ast_typed/misc.ml
@@ -342,9 +342,8 @@ let rec assert_type_expression_eq (a, b: (type_expression * type_expression)) :
       | (TC_map {k=ka;v=va} | TC_map_or_big_map {k=ka;v=va}), (TC_map {k=kb;v=vb} | TC_map_or_big_map {k=kb;v=vb})
       | (TC_big_map {k=ka;v=va} | TC_map_or_big_map {k=ka;v=va}), (TC_big_map {k=kb;v=vb} | TC_map_or_big_map {k=kb;v=vb})
         -> ok @@ ([ka;va] ,[kb;vb]) 
-      | TC_michelson_or {l=la;r=ra}, TC_michelson_or {l=lb;r=rb} -> ok @@ ([la;ra] , [lb;rb])
-      | (TC_option _ | TC_list _ | TC_contract _ | TC_set _ | TC_map _ | TC_big_map _ | TC_map_or_big_map _ | TC_arrow _| TC_michelson_or _ ),
-        (TC_option _ | TC_list _ | TC_contract _ | TC_set _ | TC_map _ | TC_big_map _ | TC_map_or_big_map _ | TC_arrow _| TC_michelson_or _ )
+      | (TC_option _ | TC_list _ | TC_contract _ | TC_set _ | TC_map _ | TC_big_map _ | TC_map_or_big_map _ | TC_arrow _ ),
+        (TC_option _ | TC_list _ | TC_contract _ | TC_set _ | TC_map _ | TC_big_map _ | TC_map_or_big_map _ | TC_arrow _ )
         -> fail @@ different_operators opa opb
       in
       if List.length lsta <> List.length lstb then
@@ -357,7 +356,7 @@ let rec assert_type_expression_eq (a, b: (type_expression * type_expression)) :
   | T_sum sa, T_sum sb -> (
       let sa' = CMap.to_kv_list sa in
       let sb' = CMap.to_kv_list sb in
-      let aux ((ka, va), (kb, vb)) =
+      let aux ((ka, {ctor_type=va;_}), (kb, {ctor_type=vb;_})) =
         let%bind _ =
           Assert.assert_true ~msg:"different keys in sum types"
           @@ (ka = kb) in
diff --git a/src/stages/4-ast_typed/types.ml b/src/stages/4-ast_typed/types.ml
index 6ded1c8a0..099469a21 100644
--- a/src/stages/4-ast_typed/types.ml
+++ b/src/stages/4-ast_typed/types.ml
@@ -19,7 +19,7 @@ type type_constant =
     | TC_timestamp
     | TC_void
 
-type te_cmap = type_expression constructor_map
+type te_cmap = ctor_content constructor_map
 and te_lmap = type_expression label_map
 and type_meta = ast_core_type_expression option
 
@@ -36,6 +36,13 @@ and arrow = {
     type2: type_expression;
   }
 
+and annot_option = string option
+
+and ctor_content = {
+    ctor_type : type_expression;
+    michelson_annotation : annot_option;
+}
+
 and type_map_args = {
     k : type_expression;
     v : type_expression;
@@ -54,7 +61,6 @@ and type_operator =
   | TC_map of type_map_args
   | TC_big_map of type_map_args
   | TC_map_or_big_map of type_map_args
-  | TC_michelson_or of michelson_or_args
   | TC_arrow of arrow
 
 
diff --git a/src/stages/common/PP.ml b/src/stages/common/PP.ml
index 3b1e2441e..1de0b6e8c 100644
--- a/src/stages/common/PP.ml
+++ b/src/stages/common/PP.ml
@@ -8,12 +8,6 @@ let constructor ppf (c:constructor') : unit =
 let label ppf (l:label) : unit =
   let Label l = l in fprintf ppf "%s" l
 
-let cmap_sep value sep ppf m =
-  let lst = CMap.to_kv_list m in
-  let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) lst in
-  let new_pp ppf (k, v) = fprintf ppf "@[<h>%a -> %a@]" constructor k value v in
-  fprintf ppf "%a" (list_sep new_pp sep) lst
-
 let record_sep value sep ppf (m : 'a label_map) =
   let lst = LMap.to_kv_list m in
   let lst = List.sort_uniq (fun (Label a,_) (Label b,_) -> String.compare a b) lst in
@@ -35,7 +29,6 @@ let tuple_or_record_sep value format_record sep_record format_tuple sep_tuple pp
     fprintf ppf format_record (record_sep value (tag sep_record)) m
 
 let list_sep_d x = list_sep x (tag " ,@ ")
-let cmap_sep_d x = cmap_sep x (tag " ,@ ")
 let tuple_or_record_sep_expr value = tuple_or_record_sep value "@[<hv 7>record[%a]@]" " ,@ " "@[<hv 2>( %a )@]" " ,@ "
 let tuple_or_record_sep_type value = tuple_or_record_sep value "@[<hv 7>record[%a]@]" " ,@ " "@[<hv 2>( %a )@]" " *@ "
 
@@ -200,6 +193,14 @@ module Ast_PP_type (PARAMETER : AST_PARAMETER_TYPE) = struct
   open Agt
   open Format
 
+  let cmap_sep value sep ppf m =
+    let lst = CMap.to_kv_list m in
+    let lst = List.sort (fun (Constructor a,_) (Constructor b,_) -> String.compare a b) lst in
+    let new_pp ppf (k, {ctor_type;_}) = fprintf ppf "@[<h>%a -> %a@]" constructor k value ctor_type in
+    fprintf ppf "%a" (list_sep new_pp sep) lst
+  let cmap_sep_d x = cmap_sep x (tag " ,@ ")
+
+
   let rec type_expression' :
          (formatter -> type_expression -> unit)
       -> formatter
@@ -231,7 +232,6 @@ module Ast_PP_type (PARAMETER : AST_PARAMETER_TYPE) = struct
       | TC_map (k, v) -> Format.asprintf "Map (%a,%a)" f k f v
       | TC_big_map (k, v) -> Format.asprintf "Big Map (%a,%a)" f k f v
       | TC_map_or_big_map (k, v) -> Format.asprintf "Map Or Big Map (%a,%a)" f k f v
-      | TC_michelson_or (k, v) -> Format.asprintf "michelson_or (%a,%a)" f k f v
       | TC_arrow (k, v) -> Format.asprintf "arrow (%a,%a)" f k f v
       | TC_contract te  -> Format.asprintf "Contract (%a)" f te
     in
diff --git a/src/stages/common/types.ml b/src/stages/common/types.ml
index 6e68736aa..5f3b9a84d 100644
--- a/src/stages/common/types.ml
+++ b/src/stages/common/types.ml
@@ -36,8 +36,10 @@ end
 module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
   open PARAMETER
 
+  type michelson_annotation = string
+
   type type_content =
-    | T_sum of type_expression constructor_map
+    | T_sum of ctor_content constructor_map
     | T_record of type_expression label_map
     | T_arrow of arrow
     | T_variable of type_variable
@@ -45,6 +47,8 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
     | T_operator of type_operator
 
   and arrow = {type1: type_expression; type2: type_expression}
+  
+  and ctor_content = {ctor_type : type_expression ; michelson_annotation : string option}
 
   and type_operator =
     | TC_contract of type_expression
@@ -54,7 +58,6 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
     | TC_map of type_expression * type_expression
     | TC_big_map of type_expression * type_expression
     | TC_map_or_big_map of type_expression * type_expression
-    | TC_michelson_or of type_expression * type_expression
     | TC_arrow of type_expression * type_expression
 
 
@@ -69,7 +72,6 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
     | TC_map (x , y) -> TC_map (f x , f y)
     | TC_big_map (x , y)-> TC_big_map (f x , f y)
     | TC_map_or_big_map (x , y)-> TC_map_or_big_map (f x , f y)
-    | TC_michelson_or (x , y)-> TC_michelson_or (f x , f y)
     | TC_arrow (x, y) -> TC_arrow (f x, f y)
 
   let bind_map_type_operator f = function
@@ -80,7 +82,6 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
     | TC_map (x , y) -> let%bind x = f x in let%bind y = f y in ok @@ TC_map (x , y)
     | TC_big_map (x , y)-> let%bind x = f x in let%bind y = f y in ok @@ TC_big_map (x , y)
     | TC_map_or_big_map (x , y)-> let%bind x = f x in let%bind y = f y in ok @@ TC_map_or_big_map (x , y)
-    | TC_michelson_or (x , y)-> let%bind x = f x in let%bind y = f y in ok @@ TC_michelson_or (x , y)
     | TC_arrow (x , y)-> let%bind x = f x in let%bind y = f y in ok @@ TC_arrow (x , y)
 
   let type_operator_name = function
@@ -91,7 +92,6 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
       | TC_map      _ -> "TC_map"
       | TC_big_map  _ -> "TC_big_map"
       | TC_map_or_big_map _ -> "TC_map_or_big_map"
-      | TC_michelson_or _ -> "TC_michelson_or"
       | TC_arrow    _ -> "TC_arrow"
 
   let type_expression'_of_string = function
@@ -131,7 +131,6 @@ module Ast_generic_type (PARAMETER : AST_PARAMETER_TYPE) = struct
     | TC_map            (x , y) -> "TC_map"          , [x ; y]
     | TC_big_map        (x , y) -> "TC_big_map"      , [x ; y]
     | TC_map_or_big_map (x , y) -> "TC_map_or_big_map"  , [x ; y]
-    | TC_michelson_or   (x , y) -> "TC_michelson_or" , [x ; y]
     | TC_arrow          (x , y) -> "TC_arrow"        , [x ; y]
 
   let string_of_type_constant = function
diff --git a/src/stages/typesystem/core.ml b/src/stages/typesystem/core.ml
index f6e362c3b..cf7dd41b8 100644
--- a/src/stages/typesystem/core.ml
+++ b/src/stages/typesystem/core.ml
@@ -15,7 +15,6 @@ type constant_tag =
   | C_variant   (* ( label , * ) … -> * *)
   | C_map       (* * -> * -> * *)
   | C_big_map   (* * -> * -> * *)
-  | C_michelson_or (* * -> * -> * *)
   | C_list      (* * -> * *)
   | C_set       (* * -> * *)
   | C_unit      (* * *)
@@ -76,11 +75,10 @@ let type_expression'_of_simple_c_constant = function
   | C_set       , [x]     -> ok @@ Ast_typed.T_operator(TC_set x)
   | C_map       , [k ; v] -> ok @@ Ast_typed.T_operator(TC_map {k ; v})
   | C_big_map   , [k ; v] -> ok @@ Ast_typed.T_operator(TC_big_map {k ; v})
-  | C_michelson_or , [l ; r] -> ok @@ Ast_typed.T_operator(TC_michelson_or {l ; r})
   | C_arrow     , [x ; y] -> ok @@ Ast_typed.T_operator(TC_arrow {type1=x ; type2=y})
   | C_record    , _lst    -> ok @@ failwith "records are not supported yet: T_record lst"
   | C_variant   , _lst    -> ok @@ failwith "sums are not supported yet: T_sum lst"
-  | (C_contract | C_option | C_list | C_set | C_map | C_big_map | C_arrow | C_michelson_or ), _ ->
+  | (C_contract | C_option | C_list | C_set | C_map | C_big_map | C_arrow ), _ ->
      failwith "internal error: wrong number of arguments for type operator"
 
   | C_unit      , [] -> ok @@ Ast_typed.T_constant(TC_unit)
diff --git a/src/test/contracts/michelson_or_tree.ligo b/src/test/contracts/michelson_or_tree.ligo
new file mode 100644
index 000000000..96e0f5850
--- /dev/null
+++ b/src/test/contracts/michelson_or_tree.ligo
@@ -0,0 +1,8 @@
+type inner_storage is michelson_or(int,"one",nat,"two")
+type storage is michelson_or (int,"three",inner_storage,"four")
+
+type return is list(operation) * storage
+
+function main (const action : unit; const store : storage) : return is block {
+  const foo : storage = (M_right ((M_left(1) : inner_storage)) : storage) ;
+} with ((nil : list(operation)), (foo: storage))
diff --git a/src/test/contracts/michelson_or_tree.mligo b/src/test/contracts/michelson_or_tree.mligo
index 6f08f67bc..943f4506c 100644
--- a/src/test/contracts/michelson_or_tree.mligo
+++ b/src/test/contracts/michelson_or_tree.mligo
@@ -1,5 +1,5 @@
-type inner_storage = (int,nat) michelson_or
-type storage = (int,inner_storage) michelson_or 
+type inner_storage = (int,"one",nat,"two") michelson_or
+type storage = (int,"three",inner_storage,"four") michelson_or 
 
 type return = operation list * storage
 
diff --git a/src/test/typer_tests.ml b/src/test/typer_tests.ml
index a29963d7e..7dd3f1f42 100644
--- a/src/test/typer_tests.ml
+++ b/src/test/typer_tests.ml
@@ -55,8 +55,9 @@ module TestExpressions = struct
       O.(make_t_ez_record [("0",t_int ()); ("1",t_string ())])
 
   let constructor () : unit result =
-    let variant_foo_bar =
-      O.[(Typed.Constructor "foo", t_int ()); (Constructor "bar", t_string ())]
+    let variant_foo_bar : (Typed.constructor' * Typed.ctor_content) list = [
+        (Typed.Constructor "foo", {ctor_type = Typed.t_int () ; michelson_annotation = None});
+        (Typed.Constructor "bar", {ctor_type = Typed.t_string () ; michelson_annotation = None}) ]
     in test_expression
       ~env:(E.env_sum_type variant_foo_bar)
       I.(e_constructor "foo" (e_int 32))