diff --git a/xpcom/glue/nsTHashtable.h b/xpcom/glue/nsTHashtable.h
index 545837309833..10218b4f7cfc 100644
--- a/xpcom/glue/nsTHashtable.h
+++ b/xpcom/glue/nsTHashtable.h
@@ -119,6 +119,11 @@ public:
    */
   uint32_t Count() const { return mTable.EntryCount(); }
 
+  /**
+   * Return true if the hashtable is empty.
+   */
+  bool IsEmpty() const { return Count() == 0; }
+
   /**
    * Get the entry associated with a key.
    * @param     aKey the key to retrieve