diff --git a/auth/cas/CAS/CAS.php b/auth/cas/CAS/CAS.php
index 975c0e58996..f9c60faea7d 100644
--- a/auth/cas/CAS/CAS.php
+++ b/auth/cas/CAS/CAS.php
@@ -32,8 +32,9 @@
 //
 // hack by Vangelis Haniotakis to handle the absence of $_SERVER['REQUEST_URI'] in IIS
 //
-if (!isset($_SERVER['REQUEST_URI'])) {
-	$_SERVER['REQUEST_URI'] = $_SERVER['SCRIPT_NAME'] . '?' . $_SERVER['QUERY_STRING'];
+$_SERVER['REQUEST_URI'] = $_SERVER['SCRIPT_NAME'];
+if (isset($_SERVER['QUERY_STRING'])) {
+    $_SERVER['REQUEST_URI'] .= '?' . $_SERVER['QUERY_STRING'];
 }
 
 //