diff --git includes/authorize.inc includes/authorize.inc
index 341fc31..bb5a6b2 100644
--- includes/authorize.inc
+++ includes/authorize.inc
@@ -83,7 +83,7 @@ function authorize_filetransfer_form($form_state) {
     $form['connection_settings']['authorize_filetransfer_default']['#options'][$name] = $backend['title'];
     $form['connection_settings'][$name] = array(
       '#type' => 'fieldset',
-      '#attributes' => array('class' => "filetransfer-$name filetransfer"),
+      '#attributes' => array('class' => array('filetransfer-$name', 'filetransfer')),
       '#title' => t('@backend connection settings', array('@backend' => $backend['title'])),
     );