diff --git a/src/as/com/threerings/util/HashMap.as b/src/as/com/threerings/util/HashMap.as
index e832c4557..7a7cc6a30 100644
--- a/src/as/com/threerings/util/HashMap.as
+++ b/src/as/com/threerings/util/HashMap.as
@@ -316,7 +316,8 @@ public class HashMap
      */
     protected function isSimple (key :Object) :Boolean
     {
-        return (key == null) || (key is String) || (key is Number) || (key is Boolean);
+        return (key == null) || (key is String) || (key is Number) || (key is Boolean) ||
+            (key is Enum);
     }
 
     /**