diff --git a/lib/client.js b/lib/client.js
index 26f2c9d9..104bcb49 100644
--- a/lib/client.js
+++ b/lib/client.js
@@ -177,8 +177,8 @@ var Util, DOM, CloudFunc, join;
         this.join                   = function(urls) {
             var prefix  = CloudCmd.PREFIX;
             
-            if (typeof urls !== 'string')
-                throw Error('urls should be string!');
+            if (!Array.isArray(urls))
+                throw Error('urls should be array!');
             
             urls = urls.map(function(url) {
                 return url.replace(prefix, '');