Your system information

• Steam client version (build number or date): Aug 21 2018, at 22:37:24 v018
• Distribution (e.g. Ubuntu): Ubuntu 18.04.1 LTS
• Opted into Steam client beta?: Yes
• Have you checked for system updates?: Yes

Please describe your issue in as much detail as possible:

When I move the mouse, the mouse's icon on the screen disappears. If you stop moving it, shows up again.

Steps for reproducing this issue:

1. Activate Steam Beta Update
2. Install Warhammer 40k: Dark Crusade (In the supported games list)
3. Run the game.
4. Happens in game and in the main menu.