diff --git a/xpcom/ds/nsHashtable.h b/xpcom/ds/nsHashtable.h
index 505b2549a2a..b3fcaba788b 100644
--- a/xpcom/ds/nsHashtable.h
+++ b/xpcom/ds/nsHashtable.h
@@ -62,6 +62,7 @@ class NS_COM nsHashKey {
     enum nsHashKeyType {
         UnknownKey,
         SupportsKey,
+        PRUint32Key,
         VoidKey,
         IDKey,
         CStringKey,
@@ -227,6 +228,31 @@ class NS_COM nsISupportsKey : public nsHashKey {
     nsresult Write(nsIObjectOutputStream* aStream) const;
 };
 
+
+class nsPRUint32Key : public nsHashKey {
+protected:
+    PRUint32 mKey;
+public:
+    nsPRUint32Key(PRUint32 key) {
+#ifdef DEBUG
+        mKeyType = PRUint32Key;
+#endif
+        mKey = key;
+    }
+
+    PRUint32 HashCode(void) const {
+        return mKey;
+    }
+
+    PRBool Equals(const nsHashKey *aKey) const {
+        return mKey == ((const nsPRUint32Key *) aKey)->mKey;
+    }
+    nsHashKey *Clone() const {
+        return new nsPRUint32Key(mKey);
+    }
+    PRUint32 GetValue() { return mKey; }
+};
+
 ////////////////////////////////////////////////////////////////////////////////
 // nsVoidKey: Where keys are void* objects that don't get refcounted.