Problem with application/octet-stream content-type

How to configure that?

the files xxx-yyy-ddd-hhh and xxx-yyy-ddd-hhh.html have the same html
code
in it.

Typing example.com/xxx-yyy-ddd-hhh.html in the browser is OK.

Typing example.com/xxx-yyy-ddd-hhh in the browser get the wronge
content-type application/octet-stream.
A text/html content-type is need.

Posted at Nginx Forum:

Nginx binds file extensions with file types:
Module ngx_http_core_module
An examples there links to
Module ngx_http_core_module

B. R.