--- a/netwerk/base/nsChannelClassifier.cpp
+++ b/netwerk/base/nsChannelClassifier.cpp
@@ -73,17 +73,20 @@ nsChannelClassifier::ShouldEnableTrackin
     }
 
     nsresult rv;
     nsCOMPtr<mozIThirdPartyUtil> thirdPartyUtil =
         do_GetService(THIRDPARTYUTIL_CONTRACTID, &rv);
     NS_ENSURE_SUCCESS(rv, rv);
 
     nsCOMPtr<nsIHttpChannelInternal> chan = do_QueryInterface(aChannel, &rv);
-    NS_ENSURE_SUCCESS(rv, rv);
+    if (NS_FAILED(rv) || !chan) {
+      LOG(("nsChannelClassifier[%p]: Not an HTTP channel", this));
+      return NS_OK;
+    }
 
     nsCOMPtr<nsIURI> topWinURI;
     rv = chan->GetTopWindowURI(getter_AddRefs(topWinURI));
     NS_ENSURE_SUCCESS(rv, rv);
 
     if (!topWinURI) {
       LOG(("nsChannelClassifier[%p]: No window URI\n", this));
     }