At the beginning of your vimrc (before your mappings), you should add:
It will change many behaviours inside vim (see help), and will certainly solve your problem.
Here is a similar question on SuperUser.
If this solution works, however it means that the
compatible option has not been automatically unset by
Vim, which however should happen in most cases (see
It probably means that you're not using a user vimrc configuration file, like
~/.vimrc. In this
case, Vim would unset the
compatible option automatically. So a better solution would be to put
your configuration in such a file (see
:h .vimrc for other possible names that Vim will be able