diff --git a/sites/all/modules/unl/unl_cas.module b/sites/all/modules/unl/unl_cas.module
index c10b5abd26047d19139e9e3679c1b16d7b249ae5..bdd3804f5e46b37689e8da4fe34d5d7a2442a0b4 100644
--- a/sites/all/modules/unl/unl_cas.module
+++ b/sites/all/modules/unl/unl_cas.module
@@ -58,7 +58,7 @@ function unl_cas_validate()
 {
 	$cas = unl_cas_get_adapter();
 
-    if ($_POST['logoutRequest']) {
+    if (array_key_exists('logoutRequest', $_POST)) {
         $cas->handleLogoutRequest($_POST['logoutRequest']);
     }