diff --git a/backup/util/ui/backup_ui_setting.class.php b/backup/util/ui/backup_ui_setting.class.php
index 9ef58656a2488..1712a7359a898 100644
--- a/backup/util/ui/backup_ui_setting.class.php
+++ b/backup/util/ui/backup_ui_setting.class.php
@@ -139,7 +139,8 @@ public function get_param_validation() {
      * @param string $label
      */
     public function set_label($label) {
-        if ((string)$label === '' || $label !== clean_param($label, PARAM_TEXT)) {
+        $label = (string)$label;
+        if ($label === '' || $label !== clean_param($label, PARAM_TEXT)) {
             throw new base_setting_ui_exception('setting_invalid_ui_label');
         }
         $this->label = $label;