diff --git a/layout/xul/nsXULPopupManager.cpp b/layout/xul/nsXULPopupManager.cpp
index 0a3d01849e4c..a61ba806da32 100644
--- a/layout/xul/nsXULPopupManager.cpp
+++ b/layout/xul/nsXULPopupManager.cpp
@@ -935,6 +935,7 @@ nsXULPopupManager::ShowPopupCallback(nsIContent* aPopup,
   item->SetParent(mPopups);
   mPopups = item;
   SetCaptureState(oldmenu);
+  NS_ENSURE_TRUE_VOID(weakFrame.IsAlive());
 
   item->UpdateFollowAnchor();