diff --git a/webapp/controller/BaseController.class.php b/webapp/controller/BaseController.class.php
index 2c0d476f..6c6f542b 100644
--- a/webapp/controller/BaseController.class.php
+++ b/webapp/controller/BaseController.class.php
@@ -55,7 +55,7 @@ class BaseController {
     {
         $net = getReqVal('_net', '');
         $zid = $net && count($net) > 3 ? $net[2] : 3;
-        return $zid < 1 || $zid > 4 ? 3 : $zid;
+        return ($zid >= 1 && $zid <= 4) ? $zid : 3;
     }
 
     public function _rspErr($errcode, $errmsg)