diff --git a/mozilla/toolkit/mozapps/update/src/nsUpdateService.js.in b/mozilla/toolkit/mozapps/update/src/nsUpdateService.js.in
index f8a486b3617..9cf6d933592 100644
--- a/mozilla/toolkit/mozapps/update/src/nsUpdateService.js.in
+++ b/mozilla/toolkit/mozapps/update/src/nsUpdateService.js.in
@@ -1596,6 +1596,7 @@ UpdateManager.prototype = {
   _addUpdate: function(update) {
     if (!update)
       return;
+    this._ensureUpdates();
     if (this._updates) {
       for (var i = 0; i < this._updates.length; ++i) {
         if (this._updates[i] &&