Setting up polipo proxy behind nginx

Question

I need to put polipo transparent proxy behind nginx reverse proxy. I need this to route trafic to specific polipo instances based on specific domains. For example, proxy-1.domain.com should be routed by nginx (proxy_pass) to first polipo instance and proxy-2.domain.com to second.

nginx:

server {
    listen          80;
    server_name     proxy-1.domain.com;

    location / {
            proxy_pass              http://polipo-1:8123;
    }
 }

But when I trying to request nginx I get polipo welcome page:

Welcome to Polipo

Welcome to Polipo

The Polipo manual.

The configuration interface.

Any help appreciated. Maybe someone can guide me to a better solution.