diff --git a/lib/Builtin.ml b/lib/Builtin.ml
index 1afdf95..c56755c 100644
--- a/lib/Builtin.ml
+++ b/lib/Builtin.ml
@@ -385,5 +385,5 @@ let check () =
   List.iter (fun (lid, (_, seen)) ->
     if !seen = Unused then
       let open Krml in
-      Warn.fatal_error "Unused replacement: %a" PrintAst.Ops.plid lid
+      KPrint.bprintf "Unused replacement: %a" PrintAst.Ops.plid lid
   ) replacements