diff --git a/plugins/kolab_2fa/lib/Kolab2FA/Driver/Yubikey.php b/plugins/kolab_2fa/lib/Kolab2FA/Driver/Yubikey.php
index b6fbf86b..7220b599 100644
--- a/plugins/kolab_2fa/lib/Kolab2FA/Driver/Yubikey.php
+++ b/plugins/kolab_2fa/lib/Kolab2FA/Driver/Yubikey.php
@@ -1,126 +1,126 @@
 <?php
 
 /**
  * Kolab 2-Factor-Authentication Yubikey driver implementation
  *
  * @author Thomas Bruederli <bruederli@kolabsys.com>
  *
  * Copyright (C) 2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
  * published by the Free Software Foundation, either version 3 of the
  * License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU Affero General Public License for more details.
  *
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
 namespace Kolab2FA\Driver;
 
 class Yubikey extends Base
 {
     public $method = 'yubikey';
 
     protected $backend;
 
     /**
      *
      */
-    public function init(array $config)
+    public function init($config)
     {
         parent::init($config);
 
         $this->user_settings += array(
             'yubikeyid' => array(
                 'type'     => 'text',
                 'editable' => true,
                 'label'    => 'secret',
             ),
         );
 
         // initialize validator
         $this->backend = new \Yubikey\Validate($this->config['apikey'], $this->config['clientid']);
 
         // set configured validation hosts
         if (!empty($this->config['hosts'])) {
             $this->backend->setHosts((array)$this->config['hosts']);
         }
 
         if (isset($this->config['use_https'])) {
             $this->backend->setUseSecure((bool)$this->config['use_https']);
         }
     }
 
     /**
      *
      */
     public function verify($code, $timestamp = null)
     {
         // get my secret from the user storage
         $keyid = $this->get('yubikeyid');
         $pass  = false;
 
         if (!strlen($keyid)) {
             // LOG: "no key registered for user $this->username"
             return false;
         }
 
         // check key prefix with associated Yubikey ID
         if (strpos($code, $keyid) === 0) {
             try {
                 $response = $this->backend->check($code);
                 $pass     = $response->success() === true;
             }
             catch (\Exception $e) {
                 // TODO: log exception
             }
         }
 
         // rcube::console('VERIFY Yubikey', $this->username, $keyid, $code, $pass);
         return $pass;
     }
 
     /**
      * @override
      */
-    public function set($key, $value)
+    public function set($key, $value, $persistent = true)
     {
         if ($key == 'yubikeyid' && strlen($value) > 12) {
             // verify the submitted code
             try {
                 $response = $this->backend->check($value);
                 if ($response->success() !== true) {
                     // TODO: report error
                     return false;
                 }
             }
             catch (\Exception $e) {
                 return false;
             }
 
             // truncate the submitted yubikey code to 12 characters
             $value = substr($value, 0, 12);
         }
 
-        return parent::set($key, $value);
+        return parent::set($key, $value, $persistent);
     }
 
     /**
      * @override
      */
     protected function set_user_prop($key, $value)
     {
         // set created timestamp
         if ($key !== 'created' && !isset($this->created)) {
             parent::set_user_prop('created', $this->get('created', true));
         }
 
         return parent::set_user_prop($key, $value);
     }
 }