Revive adserver through haproxy. SSL detection problem

[pst]

Hi,

we are using revive server in setup with haproxy. Haproxy is terminating ssl connections and it's forwarding HTTP requests to revive adserver with custom header set X_FORWARDED_PROTO = https.
From what I see the revive server doesn't recognize this header, and we have "mixed-content" problem in admin panel

In variables.php I've setup $GLOBALS['_MAX']['SSL_REQUEST'] = true, so no matter what headers are set revive should use https.

The problem is, the Revive server is still serving some content via http. Namly css files in admin panel.

Is there an other places in config files that I should modify to instruct adserver to use https ? 

Thanks.

[pst]

I should add that revive server is running on IIS 10.

Now I'm getting proper headers from haproxy:

HTTP_X_FORWARDED_PROTO => https 
HTTP_X_FORWARDED_PORT => 443 

This should trigger revive server to recognize that original request came via https but still it doesn't do that.