Redmine - Force SSL / HTTPS in Windows

Hi again!

I am now able to load my login page via https.
But when I try to login I get redirected to http://mydomain/redmine/my/page , without httpS!
When I type in https://mydomain/redmine/my/page erveything works fine.
Also inside of Redmine (after login) everything is forwarded with httpS.
When I logout I get redirected to http://mydomain/redmine/, also without httpS!

My redmine.conf looks like:

ProxyPass /redmine balancer://redminecluster
ProxyPassReverse /redmine balancer://redminecluster

Proxy balancer://redminecluster
RequestHeader set X_FORWARDED_PROTO ‘https’
BalancerMember http://127.0.0.1:3001/redmine
BalancerMember http://127.0.0.1:3002/redmine
/Proxy

So the RequestHeader is set...
Does anybody know how to fix this? Thanks in advance!