diff --git a/xuanxuan/extension/xuan/user/ext/lang/zh-cn/xuanxuan.php b/xuanxuan/extension/xuan/user/ext/lang/zh-cn/xuanxuan.php
index caa8438ff6..dc84c08716 100644
--- a/xuanxuan/extension/xuan/user/ext/lang/zh-cn/xuanxuan.php
+++ b/xuanxuan/extension/xuan/user/ext/lang/zh-cn/xuanxuan.php
@@ -1,7 +1,8 @@
 <?php
 $lang->user->tokenInvalid  = "Token 认证失败，请尝试使用密码登录。";
 
-if(strpos($_SERVER['HTTP_USER_AGENT'], 'xuanxuan') != false)
+/* When zentaourl?mode=getconfig is called, the $_SERVER does not have HTTP_USER_AGENT. */
+if(isset($_SERVER['HTTP_USER_AGENT']) and strpos($_SERVER['HTTP_USER_AGENT'], 'xuanxuan') != false)
 {
     $lang->user->errorDeny = "抱歉，您无权访问『<b>%s</b>』模块的『<b>%s</b>』功能。请联系管理员获取权限。";
 }