Mixed HTTP / HTTPS content with Gitlab behind a reverse proxy

I'm running sameersbn/docker behind a nginx reverse proxy, but I get a mixed content warning on the avatar image.

No matter what I try, it is either the mixed content warning or a too many redirects error page.
I forward my http traffic automatically in nginx with this config:

server
{
    listen 80;
    server_name myserver.com;
    return 301 https://myserver.com$request_uri;
}

server
{
    listen 443 ssl;
    server_name myserver.com;

    ssl on;
    ssl_certificate myserver.cert.combined;
    ssl_certificate_key myserver.key;
    include nginx_php.conf;

    location / {
       proxy_set_header X-Forwarded-Proto: https;
       proxy_set_header X-Forwarded-Ssl: on;
       proxy_pass http://127.0.0.1:10080;
       proxy_redirect off;
       proxy_set_header Host $host;
       proxy_set_header X-Real-IP $remote_addr;
       proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    include /etc/nginx/webapps.ssl.conf;
}

As soon as I run my gitlab container with the following options, I get the too many redirects

- GITLAB_HTTPS=true
- SSL_SELF_SIGNED=false

- GITLAB_HOST=myserver.com
- GITLAB_PORT=443
- GITLAB_SSH_PORT=22

What am I doing wrong here? And why does Gitlab try to load the avatar over http?

Start with the supplied nginx reverse-proxy configuration and the GITLAB_HTTPS, SSL_SELF_SIGNED, GITLAB_HOST, and GITLAB_PORT container options. Reproduce the mixed-content and redirect behavior, then inspect the generated avatar URL and forwarded-protocol handling; done means HTTPS works without redirect loops and avatar requests use HTTPS.