Not working for my Multisite setup

[loganrosen]

I've been trying to get this SSL-only-for-admin configuration working for my Multisite installation, and I think that this plugin could be my savior, but it doesn't appear to be working for me.

I have the following constants defined in wp-config.php:

define('FORCE_SSL_ADMIN', true);
define('HTTPS_DOMAIN_ALIAS', 'wpms.mozilla-community.org');

And I disabled all of my plugins except for WordPress MU Domain Mapping and this one. But it's not redirecting to the unmapped URL properly (http://ireland.mofostaging.net/ is a mapped domain without an SSL certificate):

$ curl -i http://ireland.mofostaging.net/wp-admin/ Location: https://ireland.mofostaging.net/wp-admin/ (among other things)

Any ideas on how to resolve this issue?