Weird headers

The main page is active in the browser but the header says 404 Not Found, maybe it's a bug?

  ~$ curl -IL http://www.bytengine.com/    
  HTTP/1.1 404 Not Found
  Server: nginx/1.1.19

    
  ~$ curl -IL http://www.bytengine.com/should_404    
  HTTP/1.1 404 Not Found
  Server: nginx/1.1.19