Change default editor to vim for _ sudo systemctl edit [unit-file] _

*[4.13.12-1-ARCH with gnome3 and gdm on Xorg]* I already have set my VISUAL and EDITOR env-vars to vim. Similarly I did try SYSTEMD_EDITOR="vim"; export SYSTEMD_EDITOR in my ~/.bashrc, to no avail. When modifying unit files in Arch (systemd) via $ sudo systemctl edit _unit_ I find myself staring at nano. Life is too short and I want vim by all means. How do I do this ?