Automatic switching of audio with external monitor

[bjasper83]

I have an external monitor that has speakers, connected using a display port cable. Until about a week or so ago, my laptop would automatically use the external speakers whenever the display port was connected, and automatically switch back to the internal laptop speakers when not connected. For some reason, that is no longer the case: I have to manually go into the Playback Devices window and set one or the other as the default playback device.

Does anyone know how to re-enable that automatic switching?

Thanks a bunch!