diff --git a/index.php b/index.php
index 9e6842e..9128bc9 100755
--- a/index.php
+++ b/index.php
@@ -54,6 +54,11 @@ $action = $config['siteurl'];
 $uploadingMethodClassBaseName = basename($uploadingMethodClass, '.php');
 $uploader                     = new $uploadingMethodClassBaseName;
 
+if (! $uploader instanceof KleejaUploader) {
+    kleeja_err('Your upload Method class is not implemented our KleejaUploader Interface');
+    exit;
+}
+
 $uploader->setAllowedFileExtensions($d_groups[$userinfo['group_id']]['exts']);
 $uploader->setUploadFieldsLimit($config['filesnum']);