diff --git a/src/as/com/threerings/presents/dobj/DEvent.as b/src/as/com/threerings/presents/dobj/DEvent.as
index b93e7fd3a..a254a227f 100644
--- a/src/as/com/threerings/presents/dobj/DEvent.as
+++ b/src/as/com/threerings/presents/dobj/DEvent.as
@@ -32,6 +32,10 @@ public /* abstract */ class DEvent
 {
     public function DEvent (targetOid :int = 0)
     {
+        // TODO: Remove when https://bugzilla.mozilla.org/show_bug.cgi?id=433103 is fixed
+        if (UNSET_OLD_ENTRY == null) {
+            UNSET_OLD_ENTRY = new DummyEntry();
+        }
         _toid = targetOid;
     }
 
@@ -112,6 +116,6 @@ public /* abstract */ class DEvent
     /** The oid of the object that is the target of this event. */
     protected var _toid :int;
 
-    protected static const UNSET_OLD_ENTRY :DSet_Entry = new DummyEntry();
+    protected static var UNSET_OLD_ENTRY :DSet_Entry;
 }
 }