diff --git a/Makefile b/Makefile
index ac1bf09..c371232 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-WABT_DIR := /home/johan/Sources/github.com/WebAssembly/wabt
+WABT_DIR := /home/johan/sources/github.com/WebAssembly/wabt
 
 WAT2WASM := $(WABT_DIR)/bin/wat2wasm
 WASM2C := $(WABT_DIR)/bin/wasm2c
diff --git a/phasm/type3/constraints.py b/phasm/type3/constraints.py
index 2fbdb42..a5017fb 100644
--- a/phasm/type3/constraints.py
+++ b/phasm/type3/constraints.py
@@ -16,11 +16,12 @@ class Error:
     This means the programmer has to make some kind of chance to the
     typing of their program before the compiler can do its thing.
     """
-    def __init__(self, msg: str) -> None:
+    def __init__(self, msg: str, *, comment: Optional[str] = None) -> None:
         self.msg = msg
+        self.comment = comment
 
     def __repr__(self) -> str:
-        return f'Error({repr(self.msg)})'
+        return f'Error({repr(self.msg)}, comment={repr(self.comment)})'
 
 class RequireTypeSubstitutes:
     """
@@ -135,10 +136,10 @@ class SameTypeConstraint(ConstraintBase):
         for typ in known_types[1:]:
             if isinstance(first_type, types.AppliedType3) and isinstance(typ, types.AppliedType3):
                 if len(first_type.args) != len(typ.args):
-                    return Error('Mismatch between applied types argument count')
+                    return Error('Mismatch between applied types argument count', comment=self.comment)
 
                 if first_type.base != typ.base:
-                    return Error('Mismatch between applied types base')
+                    return Error('Mismatch between applied types base', comment=self.comment)
 
                 for first_type_arg, typ_arg in zip(first_type.args, typ.args):
                     new_constraint_list.append(SameTypeConstraint(
@@ -148,7 +149,7 @@ class SameTypeConstraint(ConstraintBase):
                 continue
 
             if typ != first_type:
-                return Error(f'{typ:s} must be {first_type:s} instead')
+                return Error(f'{typ:s} must be {first_type:s} instead', comment=self.comment)
 
         if new_constraint_list:
             # If this happens, make CheckResult a class that can have both