IIS 10 (win2016) headers converted to lowercase when requested via HTTPS

Getting strange IIS behavior when loading pages from IIS 10.0 server via HTTPS (HTTP is OK)
1) setup VM win2016 server
2) install IIS role and ASP NET 4.5
3) create webapplication bound to both 80(HTTP) and 443(HTTPS)
4) try to load any page using HTTP -> case of response headers preserved
5) try to load any page using HTTPS -> all response headers names converted to lowercase
PS: according standarts those headers names are case sensitive.
Meaning no one browser allow you to make CORS request when server respond access-control-allow-origin instead of Access-Control-Allow-Origin e.t.c.