--- a/netwerk/ipc/PNecko.ipdl
+++ b/netwerk/ipc/PNecko.ipdl
@@ -52,15 +52,15 @@ sync protocol PNecko
 {
   manager PContentProcess;
   manages PHttpChannel;
   manages PCookieService;
 
 parent:
   __delete__();
 
-  PHttpChannel(PIFrameEmbedding iframeEmbedding);
+  PHttpChannel(nullable PIFrameEmbedding iframeEmbedding);
   PCookieService();
 };
 
 
 } // namespace net
 } // namespace mozilla