Hotkey combination does not work

[patri9ck]

I am trying to create the following hotkey to run a certain command: You can either press XF86AudioMicMute alone or alt with m or button9.

So this is what I tried:

{XF86AudioMicMute,alt + {m,button9}}
    pamixer --default-source -t && \
    [ "$(pamixer --default-source --get-mute)" = false ] && \
    notify-send 'Microphone unmuted' || \
    notify-send 'Microphone muted'

...results in:

Unknown keysym name: 'XF86AudioMicMutem'.
Unknown keysym name: 'XF86AudioMicMutebutton9'.

And...

XF86AudioMicMute,alt + {m,button9}

...ends up as:

Unknown keysym name: 'XF86AudioMicMute,alt'.
Unknown keysym name: 'XF86AudioMicMute,alt'.

Finally, now with a space after the first comma...

{XF86AudioMicMute, alt + {m,button9}}

...gives me the same:

Unknown keysym name: 'XF86AudioMicMutem'.
Unknown keysym name: 'XF86AudioMicMutebutton9'.

What is wrong here?

I know I could just separate the hotkeys, so I have two instead of one with the same commands but why is this not working?