diff --git a/src/apis.js b/src/apis.js
index a6df5811c87d..d59ed3b721f5 100644
--- a/src/apis.js
+++ b/src/apis.js
@@ -17,7 +17,7 @@ function hashKey(obj) {
   var objType = typeof obj,
       key;
 
-  if (objType == 'object' && obj !== null) {
+  if (objType == 'function' || (objType == 'object' && obj !== null)) {
     if (typeof (key = obj.$$hashKey) == 'function') {
       // must invoke on object to keep the right this
       key = obj.$$hashKey();