Firefox: fixed content scripts?

platform/firefox/vapi-background.js

@@ -30,8 +30,7 @@
 /******************************************************************************/
 
 const {classes: Cc, interfaces: Ci, utils: Cu} = Components;
-
-Cu.import('resource://gre/modules/Services.jsm');
+const {Services} = Cu.import('resource://gre/modules/Services.jsm', null);
 
 /******************************************************************************/