--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -3703,16 +3703,19 @@ bool
 ContentParent::HasNotificationPermission(const IPC::Principal& aPrincipal)
 {
   return true;
 }
 
 mozilla::ipc::IPCResult
 ContentParent::RecvShowAlert(nsIAlertNotification* aAlert)
 {
+  if (!aAlert) {
+    return IPC_FAIL_NO_REASON(this);
+  }
   nsCOMPtr<nsIPrincipal> principal;
   nsresult rv = aAlert->GetPrincipal(getter_AddRefs(principal));
   if (NS_WARN_IF(NS_FAILED(rv)) ||
       !HasNotificationPermission(IPC::Principal(principal))) {
 
       return IPC_OK();
   }