diff --git a/platform/firefox/install.rdf b/platform/firefox/install.rdf
index e63c544..7c8a804 100644
--- a/platform/firefox/install.rdf
+++ b/platform/firefox/install.rdf
@@ -17,7 +17,7 @@
         <targetApplication>
             <r:Description>
                 <id>{{ec8030f7-c20a-464f-9b0e-13a3a9e97384}}</id>
-                <minVersion>29.0</minVersion>
+                <minVersion>35.0</minVersion>
                 <maxVersion>41.0</maxVersion>
             </r:Description>
         </targetApplication>
diff --git a/platform/firefox/vapi-background.js b/platform/firefox/vapi-background.js
index 5055139..5e860e2 100644
--- a/platform/firefox/vapi-background.js
+++ b/platform/firefox/vapi-background.js
@@ -1245,7 +1245,6 @@ var httpObserver = {
             }
             if ( aWindow ) {
                 return vAPI.tabs.getTabId(aWindow
-                    .QueryInterface(Ci.nsIInterfaceRequestor)
                     .getInterface(Ci.nsIWebNavigation)
                     .QueryInterface(Ci.nsIDocShell)
                     .rootTreeItem