SSL behind load balancer

It seems that exponent-cms doesn't recognize when a user accesses the site through a load balancer that does SSL termination.

This file:
exponent-cms/exponent_constants.php

This code:

/** * URL_BASE Constant * * The URL_BASE constant is the base URL of the domain hosting the Exponent site. * It does not include the PATH_RELATIVE information. The automatic * detection code can figure out if the server is running in SSL mode or not */ if (!defined('URL_BASE')) {
define('URL_BASE', ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on') ? 'https://' : 'http://') . HOSTNAME); }

Should make another server check:

$_SERVER['HTTP_X_FORWARDED_PROTO'] should return http or https