I have some problems. Nginx doesn't work with SSI. Nginx listens 80 port (frontend), apache2 listens 81 port (backend). That is my nginx configurations:

server {
listen 80;
server_name test.dev www.test.dev;
error_log   /var/log/nginx/error.log debug;   
log_subrequest  on;

location / {
        ssi on;
        proxy_pass http://localhost:81;
        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;
        client_max_body_size       15m;
        client_body_buffer_size    128k;
   }
}

SSI include in test.dev index.php: <!--# include virtual="http:test.dev/test.html" -->

When I open test.dev/index.php I see clean page. In page source: <!--# include virtual="http:test.dev/test.html" -->

So how to enable SSI in nginx?

Can you help me?