Flask redirect ignores base URL with nginx gunicorn

Question

A redirect using:

redirect(url_for('someroute', param=val))

Is routed to:

http/someroute/val

instead of:

http://site.ip.add.ress/someroute/val

It works properly on dev (ubuntu + flask built-in server) but doesn't on production (nginx + gunicorn).

I followed this tutorial which instructs me to setup the config for nginx as follows:

server {
    location / {
        proxy_pass http://localhost:8000;
        proxy_set_header Host http://site.ip.add.ress;
        proxy_set_header X-Real-IP site.ip.add.ress;
    }
    location /static {
        alias  /home/www/flask_project/static/;
    }
}

My Flask app is as simple as the common flask hello-world stuff you see in virtually all tutorials online.

Thanks!