security/doas can't work with zsh alias

[alphachi]

I'm preparing to migrate to doas and the following commands are my test:

% cat /usr/local/etc/doas.conf
permit nopass keepenv fbsd as root
permit nopass keepenv root as root
% id -nu
fbsd
% doas id -nu
root
% echo $SHELL
/usr/local/bin/zsh
% doas echo $SHELL
/usr/local/bin/zsh
% alias
vi=vim
% doas alias
%

As this shows, doas doesn't know this alias, so "doas vi" can't invoke
installed vim.

Is this reasonable or just my mistake? How to enable zsh alias for doas?
Thanks!