diff --git a/src/transpiler/transpiler.ml b/src/transpiler/transpiler.ml
index 7da6985e9..47582e004 100644
--- a/src/transpiler/transpiler.ml
+++ b/src/transpiler/transpiler.ml
@@ -603,7 +603,7 @@ let extract_constructor (v : value) (tree : _ Append_tree.t') : (string * value
     | Leaf (k, t), v -> ok (k, v, t)
     | Node {a}, D_left v -> aux (a, v)
     | Node {b}, D_right v -> aux (b, v)
-    | _ -> simple_fail "bad constructor path"
+    | _ -> internal_assertion_fail "bad constructor path"
   in
   let%bind (s, v, t) = aux (tree, v) in
   ok (s, v, t)
@@ -617,7 +617,7 @@ let extract_tuple (v : value) (tree : AST.type_value Append_tree.t') : ((value *
         let%bind a' = aux (a, va) in
         let%bind b' = aux (b, vb) in
         ok (a' @ b')
-    | _ -> simple_fail "bad tuple path"
+    | _ -> internal_assertion_fail "bad tuple path"
   in
   aux (tree, v)
 
@@ -630,7 +630,7 @@ let extract_record (v : value) (tree : _ Append_tree.t') : (_ list) result =
         let%bind a' = aux (a, va) in
         let%bind b' = aux (b, vb) in
         ok (a' @ b')
-    | _ -> simple_fail "bad record path"
+    | _ -> internal_assertion_fail "bad record path"
   in
   aux (tree, v)
 
diff --git a/src/typer/typer.ml b/src/typer/typer.ml
index 61d2c8caf..643196e79 100644
--- a/src/typer/typer.ml
+++ b/src/typer/typer.ml
@@ -714,7 +714,7 @@ and type_expression : environment -> ?tv_opt:O.type_value -> I.expression -> O.a
       O.merge_annotation
         (Some tv)
         (Some expr'.type_annotation)
-        (simple_error "assertion failed") in
+        (internal_assertion_fail "merge_annotations (Some ...) (Some ...) failed") in
     ok {expr' with type_annotation}
 
 
@@ -729,7 +729,7 @@ and type_constant (name:string) (lst:O.type_value list) (tv_opt:O.type_value opt
 let untype_type_value (t:O.type_value) : (I.type_expression) result =
   match t.simplified with
   | Some s -> ok s
-  | _ -> simple_fail "trying to untype generated type"
+  | _ -> internal_assertion_fail "trying to untype generated type"
 
 let untype_literal (l:O.literal) : I.literal result =
   let open I in
diff --git a/vendors/ligo-utils/simple-utils/trace.ml b/vendors/ligo-utils/simple-utils/trace.ml
index c175b4149..4669f07a1 100644
--- a/vendors/ligo-utils/simple-utils/trace.ml
+++ b/vendors/ligo-utils/simple-utils/trace.ml
@@ -200,6 +200,7 @@ let prepend_info = fun info err ->
 let simple_error str () = mk_error ~title:(thunk str) ()
 let simple_info str () = mk_info ~title:(thunk str) ()
 let simple_fail str = fail @@ simple_error str
+let internal_assertion_fail str = fail @@ simple_error ("assertion failed: " ^ str)
 
 (**
    To be used when you only want to signal an error. It can be useful when