PCM volume indicator bar

I am playing music over a USB DAC which is my 2nd soundcard, so that all other non-music noice goes to the default onboard card. This works all fine, but the volume indicator bar in moc stays at 0%, even when in alsamixer the PCM volume is clearly up (and music can be heard nicely).

I have the following in ~/.moc/config

ALSADevice = "plughw:1"
ALSAMixer1 = PCM

I can control the volume without a problem with my keyboard using the following key bindings in my i3wm config file:

bindcode 122 exec amixer -c 1 set PCM 3%- unmute
bindcode 123 exec amixer -c 1 set PCM 3%+ unmute
bindcode 121 exec amixer -c 1 set PCM toggle

So, what should I do to also get the correct PCM volume indicated within moc?