diff --git a/content/xul/document/src/nsXULDocument.cpp b/content/xul/document/src/nsXULDocument.cpp
index 6eaa30047e3..b876688c974 100644
--- a/content/xul/document/src/nsXULDocument.cpp
+++ b/content/xul/document/src/nsXULDocument.cpp
@@ -2995,6 +2995,7 @@ nsXULDocument::ResumeWalk()
         if (! count)
             break;
 
+        nsCOMPtr<nsIURI> overlayURI = mCurrentPrototype->GetURI();
         nsCOMPtr<nsIURI> uri = mUnloadedOverlays[count-1];
         mUnloadedOverlays.RemoveObjectAt(count-1);
 
@@ -3008,8 +3009,21 @@ nsXULDocument::ResumeWalk()
             continue;
         if (NS_FAILED(rv))
             return rv;
-        if (shouldReturn)
+        if (shouldReturn) {
+            if (mOverlayLoadObservers.IsInitialized()) {
+                nsIObserver *obs = mOverlayLoadObservers.GetWeak(overlayURI);
+                if (obs) {
+                    // This overlay has an unloaded overlay, so it will never
+                    // notify. The best we can do is to notify for the unloaded
+                    // overlay instead, assuming nobody is already notifiable
+                    // for it. Note that this will confuse the observer.
+                    if (!mOverlayLoadObservers.GetWeak(uri))
+                        mOverlayLoadObservers.Put(uri, obs);
+                    mOverlayLoadObservers.Remove(overlayURI);
+                }
+            }
             return NS_OK;
+        }
     }
 
     // If we get here, there is nothing left for us to walk. The content