diff --git a/Source/Modules/javascript.cxx b/Source/Modules/javascript.cxx
index 31576bd93..98f6d801f 100644
--- a/Source/Modules/javascript.cxx
+++ b/Source/Modules/javascript.cxx
@@ -1575,7 +1575,7 @@ void JSCEmitter::marshalInputArgs(Node *n, ParmList *parms, Wrapper *wrapper, Ma
       Printf(arg, "argv[%d]", i);
       break;
     default:
-      Printf(stdout, "Illegal state.");
+      Printf(stderr, "Illegal MarshallingMode.");
       SWIG_exit(EXIT_FAILURE);
     }
     tm = emitInputTypemap(n, p, wrapper, arg);
@@ -2213,7 +2213,7 @@ void V8Emitter::marshalInputArgs(Node *n, ParmList *parms, Wrapper *wrapper, Mar
       Printf(arg, "args[%d]", i);
       break;
     default:
-      Printf(stdout, "Illegal state.");
+      Printf(stderr, "Illegal MarshallingMode.");
       SWIG_exit(EXIT_FAILURE);
     }