diff --git a/gcc/rust/typecheck/rust-tyty.cc b/gcc/rust/typecheck/rust-tyty.cc
index 26c061258cd2..467bf1c21753 100644
--- a/gcc/rust/typecheck/rust-tyty.cc
+++ b/gcc/rust/typecheck/rust-tyty.cc
@@ -597,7 +597,7 @@ BaseType::monomorphized_clone () const
     {
       std::vector<TyTy::FnParam> cloned_params;
       for (auto &p : fn->get_params ())
-	cloned_params.push_back (p.clone ());
+	cloned_params.push_back (p.monomorphized_clone ());
 
       BaseType *retty = fn->get_return_type ()->monomorphized_clone ();
       return new FnType (fn->get_ref (), fn->get_ty_ref (), fn->get_id (),
diff --git a/gcc/rust/typecheck/rust-tyty.h b/gcc/rust/typecheck/rust-tyty.h
index c896d1e03b75..167d425840e6 100644
--- a/gcc/rust/typecheck/rust-tyty.h
+++ b/gcc/rust/typecheck/rust-tyty.h
@@ -791,6 +791,11 @@ class FnParam
   void set_type (BaseType *new_type) { type = new_type; }
 
   FnParam clone () const
+  {
+    return FnParam (pattern->clone_pattern (), type->clone ());
+  }
+
+  FnParam monomorphized_clone () const
   {
     return FnParam (pattern->clone_pattern (), type->monomorphized_clone ());
   }