nginx 404 page shows wrong version - nginx

Question

My nginx version is 1.4.6:
root#jung-digital:~# nginx -v
nginx version: nginx/1.4.6 (Ubuntu)
I've set up a reverse proxy to a server with version 1.8.0 on it, as confirmed by hitting an invalid path on that server.
However, my reverse proxy is showing an HTML page when attempting to use the reverse proxy saying:
404 Not Found
nginx/1.4.1 (Ubuntu)
What in the world is going on? Neither my reverse proxy server nor the target server for the proxy are using nginx 1.4.1.
For those curious, here are the relevant sections from my nginx.conf:
upstream ireport_dyndns {
server ireport.somedomain.org;
}
...
server {
listen 80;
server_name ireport.somedomain2.com;
access_log /var/log/nginx/ireport.access.log;
root /var/www/ireport.somedomain2.com/dist;
index index.html index.htm;
location /api/ {
add_header 'Access-Control-Allow-Origin' '*';
add_header 'Access-Control-Allow-Methods' 'POST,GET,OPTIONS';
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-NginX-proxy true;
proxy_pass http://ireport_dyndns/api/;
proxy_ssl_session_reuse off;
proxy_set_header Host $http_host;
proxy_redirect off;
}
}

Answer 1

Discovered that this must be a bug in nginx. The proxied server had a configuration change that was checking the HOST header and my proxy_pass settings were sending the wrong HOST and therefore the proxied server was returning a 404.
The response from the proxied server specifies NGINX 1.8.0 in the headers but 1.4.1 in the body.
Bug in nginx.