diff --git a/lib/client.js b/lib/client.js
index f8a66d6d..26f2c9d9 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -177,7 +177,8 @@ var Util, DOM, CloudFunc, join;
         this.join                   = function(urls) {
             var prefix  = CloudCmd.PREFIX;
             
-            Util.check(arguments, ['urls']);
+            if (typeof urls !== 'string')
+                throw Error('urls should be string!');
             
             urls = urls.map(function(url) {
                 return url.replace(prefix, '');