diff --git a/mozilla/content/xul/document/src/nsXULDocument.cpp b/mozilla/content/xul/document/src/nsXULDocument.cpp
index 1d049c8a667..612daad9bab 100644
--- a/mozilla/content/xul/document/src/nsXULDocument.cpp
+++ b/mozilla/content/xul/document/src/nsXULDocument.cpp
@@ -2673,8 +2673,8 @@ nsXULDocument::LoadOverlay(const nsAString& aURL, nsIObserver* aObserver)
     }
     PRBool shouldReturn;
     rv = LoadOverlayInternal(uri, PR_TRUE, &shouldReturn);
-    if (NS_FAILED(rv))
-      mOverlayLoadObservers.Remove(uri); // remove the observer if LoadOverlayInternal generated an error
+    if (NS_FAILED(rv) && mOverlayLoadObservers.IsInitialized())
+        mOverlayLoadObservers.Remove(uri); // remove the observer if LoadOverlayInternal generated an error
     return rv;
 }