Nginx, charset directive not working when sending 301 redirect

Question

I have set the charset to 'utf-8' in the nginx.conf file under the http directive. It looks like this:

http {
  charset utf-8;
}

I have two server directives. One for example.com, and one for www.example.com. They look like this.

server {
        listen 80;
        server_name example.com;
        root /usr/share/nginx/html;
        return 301 http://www.example.com$request_uri;
}
server {
        listen 80;
        server_name www.example.com;
        root /usr/share/nginx/html;
        index index.html;
        location /{
                try_files $uri $uri/ =404;
        }
}

However, an initial request to example.com does not seem to present the charset type after the Content-Type HTTP header. Here are the response headers:

$ curl example.com -I --progress-bar
HTTP/1.1 301 Moved Permanently
Server: nginx
Date: Thu, 10 Jul 2014 05:10:42 GMT
Content-Type: text/html
Content-Length: 178
Connection: keep-alive
Location: http://www.example.com/

$ curl www.example.com -I --progress-bar
HTTP/1.1 200 OK
Server: nginx
Date: Thu, 10 Jul 2014 05:13:30 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 123
Last-Modified: Tue, 08 Jul 2014 00:55:38 GMT
Connection: keep-alive
ETag: "53bb418a-7b"
Accept-Ranges: bytes

Why isn't the charset being set in the non-www server?

Answer 1

Since you did not define custom error page for 301 error, nginx sends it's built-in special page with predefined headers.

See https://github.com/nginx/nginx/blob/master/src/http/ngx_http_special_response.c#L646