P2418HZM, volume keeps reverting to default setting

The volume on my P2418HZM keep reverting to its default setting (about two-thirds of the scale) everytime it goes to sleep or turns off. I want it to stay at the maximum level, as even on maximum it is quite quiet. Is there any way to set it forever and not having it impacted by sleep or power-off events? Connection via DisplayPort, if that is relevant.

Thank you.