--- a/dom/html/nsDOMStringMap.cpp
+++ b/dom/html/nsDOMStringMap.cpp
@@ -121,21 +121,23 @@ nsDOMStringMap::NamedSetter(const nsAStr
   }
 }
 
 void
 nsDOMStringMap::NamedDeleter(const nsAString& aProp, bool& found)
 {
   // Currently removing property, attribute is already removed.
   if (mRemovingProp) {
+    found = false;
     return;
   }
   
   nsAutoString attr;
   if (!DataPropToAttr(aProp, attr)) {
+    found = false;
     return;
   }
 
   nsCOMPtr<nsIAtom> attrAtom = do_GetAtom(attr);
   MOZ_ASSERT(attrAtom, "Should be infallible");
 
   found = mElement->HasAttr(kNameSpaceID_None, attrAtom);