diff --git a/login/logout.php b/login/logout.php
index 33a8192d1f7..7d94ab3f473 100644
--- a/login/logout.php
+++ b/login/logout.php
@@ -4,7 +4,7 @@
     require("../config.php");
 
     add_to_log("Logged out");
-    unset($USER);
+    $USER = NULL;
     redirect($HTTP_REFERER);
     exit;