diff --git a/lib/urlbarbutton.js b/lib/urlbarbutton.js
index 71caf57..ebb6e55 100644
--- a/lib/urlbarbutton.js
+++ b/lib/urlbarbutton.js
@@ -30,7 +30,7 @@ UrlbarButton = function (options) {
       button, window;
 
     for (window in winUtils.windowIterator()) {
-      if (!href || href === getPageDocument(window.gBrowser.selectedTab).location.href) {
+      if (!href || (window.gBrowser && href === getPageDocument(window.gBrowser.selectedTab).location.href)) {
         button = window.document.getElementById(options.id);
         if (button) {
           elements.push(button);
@@ -136,7 +136,7 @@ UrlbarButton = function (options) {
             console.log('LocationChange!');
             options.onLocationChange.call(tabbrowser.contentDocument, doc.location.href, visibilityCallback.bind(undefined, doc.location.href));
           }
-        }, Ci.nsIWebProgress.NOTIFY_LOCATION);
+        });
       }
     },
     onUntrack: function (tabbrowser) {