Bad Request (400) - Django, Nginx, Gunicorn on Debian 7

I’m trying to run Django on Nginx + Unicorn (Debian 7) as described in this tutorial: https://www.digitalocean.com/community/tutorials/how-to-deploy-a-local-django-app-to-a-vps

This is how my Nginx looks like:

server{
        server_name 146.185.185.212;

        access_log off;

        location /static/ {
                alias opt/myenv/static/;
        }

        location / {
                proxy_pass http://127.0.0.1:8001;
                proxy_set_header X-Forwarded-Host $server_name;
                proxy_set_header X-Real-IP $remote_addr;
                add_header P3P 'CP="ALL DSP COR PSAa PSDa OUR NOR ONL UNI COM N$
        }
}

This is how I start Gunicorn:

gunicorn --bind 127.0.0.1:8001 projname.wsgi:application

The problem is that i keep getting : Bad Request (400) in the browser.

Does anyone have any clue on how to fix this?