xcape does not work properly when trying to emit Multi_key

[sersorrel]

I'm trying to make my super key act as compose when tapped, but xcape seems unwilling to ever emit Multi_key – apparently it interprets Multi_key as ISO_Level3_Shift, e.g.:

$ xcape -d -e 'ISO_Level3_Shift=Multi_key'
Assigned mapping from "ISO_Level3_Shift" ( keysym 0xfe03, key code 92)
to "ISO_Level3_Shift" (keysym 0xfe03, key code 108)

This happens regardless of what key I put on the left-hand side, as far as I can tell.