I'm trying to get a maintenance page working for my site. I added the following to the server block:

error_page 503 /maintenance.html;
return 503;

This serves 503 but with default nginx 503 error page.

The following works okay, but I don't understand why the above doesn't show the custom 503 page?

error_page 503 @503;
return 503;
location @503 {
try_files /maintenance.html =503;
}

Thanks

Dave