diff --git a/embedding/components/printingui/ipc/PPrinting.ipdl b/embedding/components/printingui/ipc/PPrinting.ipdl
index 0d8380f19e13..095aefac4bf0 100644
--- a/embedding/components/printingui/ipc/PPrinting.ipdl
+++ b/embedding/components/printingui/ipc/PPrinting.ipdl
@@ -23,7 +23,7 @@ sync protocol PPrinting
 parent:
   sync ShowProgress(PBrowser browser,
                     PPrintProgressDialog printProgressDialog,
-                    PRemotePrintJob remotePrintJob,
+                    nullable PRemotePrintJob remotePrintJob,
                     bool isForPrinting)
     returns(bool notifyOnOpen,
             nsresult rv);