diff --git a/library/think/Request.php b/library/think/Request.php
index ff17f42b..21f92ad7 100644
--- a/library/think/Request.php
+++ b/library/think/Request.php
@@ -722,7 +722,7 @@ class Request
             return true;
         } elseif (isset($_SERVER['HTTP_X_WAP_PROFILE']) || isset($_SERVER['HTTP_PROFILE'])) {
             return true;
-        } elseif (preg_match('/(blackberry|configuration\/cldc|hp |hp-|htc |htc_|htc-|iemobile|kindle|midp|mmp|motorola|mobile|nokia|opera mini|opera |Googlebot-Mobile|YahooSeeker\/M1A1-R2D2|android|iphone|ipod|mobi|palm|palmos|pocket|portalmmm|ppc;|smartphone|sonyericsson|sqh|spv|symbian|treo|up.browser|up.link|vodafone|windows ce|xda |xda_)/i', $_SERVER['HTTP_USER_AGENT'])) {
+        } elseif (isset($_SERVER['HTTP_USER_AGENT']) && preg_match('/(blackberry|configuration\/cldc|hp |hp-|htc |htc_|htc-|iemobile|kindle|midp|mmp|motorola|mobile|nokia|opera mini|opera |Googlebot-Mobile|YahooSeeker\/M1A1-R2D2|android|iphone|ipod|mobi|palm|palmos|pocket|portalmmm|ppc;|smartphone|sonyericsson|sqh|spv|symbian|treo|up.browser|up.link|vodafone|windows ce|xda |xda_)/i', $_SERVER['HTTP_USER_AGENT'])) {
             return true;
         } else {
             return false;