Why GoDaddy custom domain redirects to Heroku's appid.herokuapp.com?

I am trying to setup a custom domain with Heroku.

Here is the setup I did for my wikinames.org domain in my GoDaddy account:

• DNS zone:
  • @ A 50.63.202.1
  • www CNAME myappid.herokuapp.com
• Forwarding (for naked domain support):
  • from: http://wikinames.org to: http://www.wikinames.org, 301 (permanent), forward only

Once I go to http://www.wikinames.org, I observe the following:

1. request remote address: 23.21.223.98:80, status Code: 301 Moved Permanently
2. response header: Location: https://wikinames-org.herokuapp.com/index.php?title=Main_Page (I've installed MediaWiki, but $wgServer there is equal to http://www.wikinames.org).

Why does it redirect me to wikinames-org.herokuapp.com?

Upd. Looks like it happens because of ip 50.63.202.1 used. But if I delete this record, then naked domain stops working, but www version still redirects to https://wikinames-org.herokuapp.com.

Upd2. Looks like enabling of masking could help me, but seems it will work only with www case.