diff --git a/usr/local/www/interfaces_gre.php b/usr/local/www/interfaces_gre.php
index 6a9c3cf17e..de2992b01f 100644
--- a/usr/local/www/interfaces_gre.php
+++ b/usr/local/www/interfaces_gre.php
@@ -40,6 +40,7 @@
 ##|-PRIV
 
 require("guiconfig.inc");
+require_once("functions.inc");
 
 if (!is_array($config['gres']['gre']))
 	$config['gres']['gre'] = array();