Display power management doesn't work with Firefox media playback

I can't watch any videos in Firefox without the display switching off, even with "Presentation Mode" enabled. It works fine with other programs like MPV with presentation mode disabled.

Here are my settings:

1. Blank - 30 minutes
2. Sleep - Never
3. Switch off after - 2 minutes

System info:

• OS: Arch Linux
• xfce4-power-manager 4.18.2
• firefox 119.0-1