diff --git a/Compiler/runtime/systemimpl.c b/Compiler/runtime/systemimpl.c
index 916855e80fb..4f228e87f28 100644
--- a/Compiler/runtime/systemimpl.c
+++ b/Compiler/runtime/systemimpl.c
@@ -406,7 +406,7 @@ RML_BEGIN_LABEL(System__stringReplace)
     RML_TAILCALLK(rmlFC);
   }
   rmlA0 = (void*) mk_scon(res);
-  /* free(res); */
+  free(res);
   RML_TAILCALLK(rmlSC);
 }
 RML_END_LABEL