First of all, I checked "How to prevent my screens from turning off, when the screen is locked?" but that didn't help.
The laptop is set to not suspend no matter if it's running via battery or AC. Under "Brightness & Lock", the option "Turn screen off when inactive for" is set to "Never". Brightness is set to 100% and dimming is enabled.
When I lock the machine however, the display fades to blank and then the screen goes off. How do I prevent this?