What version you are using? mine are worked fine
$ vim -version VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Aug 22 2017 12:33:17)
Same: $ vim --version VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Aug 22 2017 12:33:17)
If you don't mind, what is your "$ env | grep TERM" output ?
xterm-256color
Frédéric