diff --git a/lib/drivers/kolab/kolab_file_storage.php b/lib/drivers/kolab/kolab_file_storage.php
--- a/lib/drivers/kolab/kolab_file_storage.php
+++ b/lib/drivers/kolab/kolab_file_storage.php
@@ -971,6 +971,12 @@
             throw new Exception("Storage error. Unable to get folders list.", file_storage::ERROR);
         }
 
+        // when the file storage has been disabled, return an empty list of folders otherwise
+        // inaccessible folders will be listed
+        if ($this->rc->config->get('fileapi_backend_storage_disabled')) {
+            return array();
+        }
+
         // create/subscribe 'Files' folder in case there's no folder of type 'file'
         if (empty($folders) && !$unsubscribed && !strlen($root)) {
             $default = 'Files';