diff --git a/extensions/firefox/components/PdfStreamConverter.js b/extensions/firefox/components/PdfStreamConverter.js
index f0252575a..1cb9c7a6d 100644
--- a/extensions/firefox/components/PdfStreamConverter.js
+++ b/extensions/firefox/components/PdfStreamConverter.js
@@ -386,21 +386,19 @@ ChromeActions.prototype = {
     var message = getLocalizedString(strings, 'unsupported_feature');
 
     var notificationBox = null;
-    // Multiple browser windows can be opened, finding one for notification box
-    var windowsEnum = Services.wm
-                      .getZOrderDOMWindowEnumerator('navigator:browser', true);
-    while (windowsEnum.hasMoreElements()) {
-      var win = windowsEnum.getNext();
-      if (win.closed)
-        continue;
-      var browser = win.gBrowser.getBrowserForDocument(domWindow.top.document);
-      if (browser) {
-        // right window/browser is found, getting the notification box
-        notificationBox = win.gBrowser.getNotificationBox(browser);
-        break;
-      }
-    }
-    if (!notificationBox) {
+    try {
+      // Based on MDN's "Working with windows in chrome code"
+      var mainWindow = domWindow
+        .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
+        .getInterface(Components.interfaces.nsIWebNavigation)
+        .QueryInterface(Components.interfaces.nsIDocShellTreeItem)
+        .rootTreeItem
+        .QueryInterface(Components.interfaces.nsIInterfaceRequestor)
+        .getInterface(Components.interfaces.nsIDOMWindow);
+      var browser = mainWindow.gBrowser
+                              .getBrowserForDocument(domWindow.top.document);
+      notificationBox = mainWindow.gBrowser.getNotificationBox(browser);
+    } catch (e) {
       log('Unable to get a notification box for the fallback message');
       return;
     }