diff --git a/lib/model/activityobject.js b/lib/model/activityobject.js
index <HASH>..<HASH> 100644
--- a/lib/model/activityobject.js
+++ b/lib/model/activityobject.js
@@ -392,9 +392,9 @@ ActivityObject.ensureObject = function(obj, callback) {
 };
 
 ActivityObject.isReference = function(value) {
-    var refKeys = ["id", "objectType", "updated", "published", "_uuid"],
+    var refKeys = ["id", "objectType", "updated", "published", "_uuid", "_created"],
         nonRef = _.difference(_.keys(value), refKeys);
-    
+
     return (nonRef.length === 0);
 };
Add _created to nonRef keys