--- a/dom/apps/src/AppDownloadManager.jsm
+++ b/dom/apps/src/AppDownloadManager.jsm
@@ -3,17 +3,20 @@
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cu = Components.utils;
 
-Cu.import("resource://gre/modules/FreeSpaceWatcher.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "FreeSpaceWatcher",
+                                  "resource://gre/modules/FreeSpaceWatcher.jsm");
 
 this.EXPORTED_SYMBOLS = ["AppDownloadManager"];
 
 function debug(aMsg) {
   //dump("-*-*- AppDownloadManager.jsm : " + aMsg + "\n");
 }
 
 this.AppDownloadManager = {