Django app under suburl (reversed nginx + ISA), part of the url is being repeated

Question

Pardon me if this is not the right place to ask.

I have a django app served by Gunicorn, which is reversed by NginX and this one is being reversed by an ISA server, so I have the following:

ISA --> Nginx --> Gunicorn

ISA reverses www.mydomain.com/some/path/here to Nginx, and this one reverses /myapp to Gunicorn (nginx and gunicorn are on the same server).

The problem is with the url, for instance the base url to access this apps is

www.mydomain.com/some/path/here/myapp/

When there's an action in a django view like redirect e.g: redirect(reverse('start')), the url should be

www.mydomain.com/some/path/here/myapp/start/

but I get

www.mydomain.com/some/path/here/some/path/here/myapp/start/

As you can see some/path/here/ is being repeated, I'm assuming this is done by the ISA server, but I'm not sure about this. What am I doing wrong here?

In my settings.py I have:

BASE_PATH = '/some/path/here'
FORCE_SCRIPT_NAME = BASE_PATH + '/myapp'
LOGIN_URL = FORCE_SCRIPT_NAME + '/loginhere/'

urls.py:

...
url(r'^start/', 'testapp.views.start', name='start'),
...

My nginx.conf:

user www-data;
worker_processes  1;

error_log  /var/log/nginx/error.log;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
}

http {
    include       /etc/nginx/mime.types;

    access_log /var/log/nginx/access.log;

    sendfile        on;
    keepalive_timeout  65;
    tcp_nodelay        on;

    gzip  on;
    gzip_disable "MSIE [1-6]\.(?!.*SV1)";

    upstream wawared {
        server 127.0.0.1:8000;
    }

    server {
        listen 80;
        server_name localhost;            

        access_log  /var/log/nginx/wawared.access.log;
        error_log   /var/log/nginx/wawared.error.log;

        location /static {
            root /path/to/static/files;
            expires 1d;
            gzip on;
        }

        location /myapp/ {
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Host $http_host;
            proxy_pass  http://127.0.0.1:8000/;
            proxy_redirect off;
        }
    }
}