SIGUSR1 doesn't disable gammastep

Starting gammastep from the command line and sending SIGUSR1 to it (e.g. via pkill -USR1 gammastep) should disable it, but instead nothing happens. This is with the 2.0 release of gammstep under sway 1.5 on Arch Linux.

Notably, the Enabled toggle in gammastep-indicator works as expected. This is puzzling, since from the source it looks like gammastep-indicator simply spawns an instance of gammastep and communicates with it via SIGUSR1.

I should probably add that things work as expected with redshift 1.12 (in X11).