--- a/services/sync/modules/engines.js
+++ b/services/sync/modules/engines.js
@@ -107,23 +107,16 @@ Engine.prototype = {
   // _storeObj, and _trackerObj should to be overridden in subclasses
 
   _storeObj: Store,
   _trackerObj: Tracker,
 
   get enabled() Utils.prefs.getBoolPref("engine." + this.name),
   get score() this._tracker.score,
 
-  get _os() {
-    let os = Cc["@mozilla.org/observer-service;1"].
-      getService(Ci.nsIObserverService);
-    this.__defineGetter__("_os", function() os);
-    return os;
-  },
-
   get _store() {
     let store = new this._storeObj();
     this.__defineGetter__("_store", function() store);
     return store;
   },
 
   get _tracker() {
     let tracker = new this._trackerObj();