| Index: lib/child/elemHide.js | 
| =================================================================== | 
| --- a/lib/child/elemHide.js | 
| +++ b/lib/child/elemHide.js | 
| @@ -364,17 +364,17 @@ let observer = { | 
| // Ignore NS_ERROR_ILLEGAL_VALUE - it will be thrown if we try to add | 
| // the stylesheet multiple times to the same document (the observer | 
| // will be notified twice for some documents). | 
| if (e.result != Cr.NS_ERROR_ILLEGAL_VALUE) | 
| throw e; | 
| } | 
| } | 
|  | 
| -        let host = subject.location.hostname; | 
| +        let host = window.location.hostname; | 
| if (host) | 
| { | 
| try | 
| { | 
| let suffix = "=" + encodeURIComponent(host); | 
| if (specificOnly) | 
| suffix += "&specificonly"; | 
| utils.loadSheetUsingURIString(this.styleURL.spec + suffix, | 
|  |