Global redirect fails to run at all if scriptname is not /index.php

Global redirect stopped working for me after updating to 1.3.1
the issue is if ($_SERVER['SCRIPT_NAME'] != '/index.php') return false;

the problem is that the script name is NOT guaranteed to be /index.php in a multisite multidrupal webhosting environment.

my script name is /drupal-5.10/index.php
(the drupal version is hidden by modrewrite)

different sites can be on drupal 4,5,6,7 as required and global redirect breaks!!
so i use
if (!strpos($_SERVER['SCRIPT_NAME'], '/index.php')) return false;

please advise