diff --git a/js/rhino/src/org/mozilla/javascript/resources/Messages.properties b/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
index 007d2ab10fc..2fb9a2f7d7f 100644
--- a/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
+++ b/js/rhino/src/org/mozilla/javascript/resources/Messages.properties
@@ -423,10 +423,10 @@ msg.return.inconsistent =\
   return statement is inconsistent with previous usage
 
 msg.generator.returns =\
-  generator function {0} returns a value
+  TypeError: generator function {0} returns a value
 
 msg.anon.generator.returns =\
-  anonymous generator function returns a value
+  TypeError: anonymous generator function returns a value
 
 msg.syntax =\
     syntax error