diff --git a/src/ligo/TODO.txt b/src/ligo/TODO.txt
index ef5f79d1e..210cb0637 100644
--- a/src/ligo/TODO.txt
+++ b/src/ligo/TODO.txt
@@ -3,6 +3,8 @@
 ## Back-end
 
 - Replace Mini_c environments with stacks
+  + Compiler_environment : bad pack make first element deepest
+  + Add types to pack and unpack
 - Think about Coq
 
 ## Amendments
diff --git a/src/ligo/compiler/compiler_environment.ml b/src/ligo/compiler/compiler_environment.ml
index 2f99d0a5b..c6980ee06 100644
--- a/src/ligo/compiler/compiler_environment.ml
+++ b/src/ligo/compiler/compiler_environment.ml
@@ -144,13 +144,64 @@ let pack : environment -> michelson result = fun e ->
   let%bind () =
     trace_strong (simple_error "pack empty env") @@
     Assert.assert_true (List.length e <> 0) in
-  ok @@ seq @@ List.map (Function.constant i_pair) @@ List.tl e
+  let code = seq @@ List.map (Function.constant i_pair) @@ List.tl e in
+
+  let%bind () =
+    let%bind (Stack.Ex_stack_ty input_stack_ty) = Compiler_type.Ty.environment e in
+    let repr = Environment.closure_representation e in
+    let%bind (Ex_ty output_ty) = Compiler_type.Ty.type_ repr in
+    let output_stack_ty = Stack.(output_ty @: nil) in
+    let error () =
+      let title () = "error producing Env.pack" in
+      let content () = Format.asprintf ""
+      in
+      ok @@ (error title content) in
+    let%bind _ =
+      Trace.trace_tzresult_lwt_r error @@
+      Memory_proto_alpha.parse_michelson code
+        input_stack_ty output_stack_ty in
+    ok ()
+  in
+
+  ok code
 
 let unpack : environment -> michelson result = fun e ->
   let%bind () =
     trace_strong (simple_error "unpack empty env") @@
     Assert.assert_true (List.length e <> 0) in
-  ok @@ seq @@ List.map (Function.constant i_unpair) @@ List.tl e
+
+  let l = List.length e - 1 in
+  let rec aux n =
+    match n with
+    | 0 -> seq []
+    | n -> seq [
+        i_unpair ;
+        dip (aux (n - 1)) ;
+      ] in
+  let code = aux l in
+
+  let%bind () =
+    let%bind (Stack.Ex_stack_ty output_stack_ty) = Compiler_type.Ty.environment e in
+    let repr = Environment.closure_representation e in
+    let%bind (Ex_ty input_ty) = Compiler_type.Ty.type_ repr in
+    let input_stack_ty = Stack.(input_ty @: nil) in
+    let error () =
+      let title () = "error producing Env.unpack" in
+      let content () = Format.asprintf "\nEnvironment:%a\nType Representation:%a\nCode:%a\n"
+          PP.environment e
+          PP.type_ repr
+          Micheline.Michelson.pp code
+      in
+      ok @@ (error title content) in
+    let%bind _ =
+      Trace.trace_tzresult_lwt_r error @@
+      Memory_proto_alpha.parse_michelson code
+        input_stack_ty output_stack_ty in
+    ok ()
+  in
+
+  ok code
+
 
 let pack_select : environment -> string list -> michelson result = fun e lst ->
   let module L = Logger.Stateful() in
@@ -206,10 +257,10 @@ let pack_select : environment -> string list -> michelson result = fun e lst ->
   ok code
 
 let add_packed_anon : environment -> type_value -> michelson result = fun e type_value ->
-  let code = i_pair in
+  let code = seq [i_pair] in
 
   let%bind () =
-    let error () = ok @@ simple_error "error producing Env.get" in
+    let error () = ok @@ simple_error "error producing add packed" in
     let%bind (Ex_ty input_ty) = Compiler_type.Ty.environment_representation e in
     let e' = Environment.add ("_add_packed_anon" , type_value) e in
     let%bind (Ex_ty output_ty) = Compiler_type.Ty.environment_representation e' in
diff --git a/src/ligo/compiler/compiler_program.ml b/src/ligo/compiler/compiler_program.ml
index cbaf01ce0..1bd8fd6ec 100644
--- a/src/ligo/compiler/compiler_program.ml
+++ b/src/ligo/compiler/compiler_program.ml
@@ -130,23 +130,31 @@ and translate_expression ?(first=false) (expr:expression) (env:environment) : (m
       | T_deep_closure (small_env, input_ty , _) -> (
           trace (simple_error "Compiling deep closure application") @@
           let%bind (arg' , env') = translate_expression arg env in
-          let%bind (f' , _) = translate_expression f env' in
+          let%bind (f' , env'') = translate_expression f env' in
+          let%bind f_ty = Compiler_type.type_ f.type_value in
           let%bind append_closure = Compiler_environment.add_packed_anon small_env input_ty in
           let error =
             let error_title () = "michelson type-checking closure application" in
             let error_content () =
-              Format.asprintf "Env : %a\nclosure : %a\narg : %a\n"
+              Format.asprintf "\nEnv. %a\nEnv'. %a\nEnv''. %a\nclosure. %a ; %a ; %a\narg. %a\n"
                 PP.environment env
-                PP.expression_with_type f
+                PP.environment env'
+                PP.environment env''
+                PP.expression_with_type f Michelson.pp f_ty Michelson.pp f'
                 PP.expression_with_type arg
             in
             error error_title error_content
           in
           trace error @@
           return @@ seq [
+            i_comment "closure application" ;
+            i_comment "arg" ;
             arg' ;
+            i_comment "f'" ;
             f' ; i_unpair ;
-            dip @@ append_closure ;
+            i_comment "append" ;
+            dip @@ seq [i_swap ; append_closure] ;
+            i_comment "exec" ;
             i_swap ; i_exec ;
           ]
         )
@@ -190,8 +198,7 @@ and translate_expression ?(first=false) (expr:expression) (env:environment) : (m
       in
       let error =
         let title () = "error compiling constant" in
-        let content () = L.get ()
-        in
+        let content () = L.get () in
         error title content in
       trace error @@
       return code