GPIO bininding and how to avoid starting OpenHab as root

When I start OpenHab as root GPIO Bindning work ok but when I start as openhab there are some problems with permissions.
There are many article on Internet and people propose add openhab user to gpio group but I have Openhabian (SD image for Raspberry) and there was no such group. Because of that I did following steps:

groupadd gpio
adduser openhab gpio 
chgrp -R gpio /sys/class/gpio

but it does not help and still I have the problem with permissions.
Any suggestion what is missing?