--- a/xpcom/glue/nsClassHashtable.h
+++ b/xpcom/glue/nsClassHashtable.h
@@ -24,16 +24,18 @@ template<class KeyClass, class T>
 class nsClassHashtable
   : public nsBaseHashtable<KeyClass, nsAutoPtr<T>, T*>
 {
 public:
   typedef typename KeyClass::KeyType KeyType;
   typedef T* UserDataType;
   typedef nsBaseHashtable<KeyClass, nsAutoPtr<T>, T*> base_type;
 
+  using base_type::IsEmpty;
+
   nsClassHashtable() {}
   explicit nsClassHashtable(uint32_t aInitLength)
     : nsBaseHashtable<KeyClass, nsAutoPtr<T>, T*>(aInitLength)
   {
   }
 
   /**
    * Looks up aKey in the hash table. If it doesn't exist a new object of