Can't switch layouts with super+space when password entry active in GDM with GNOME Shell 43.1

With gnome-shell 43.1 and mutter 43.1 - not sure which caused the problem - switching keyboard layouts with super+space does not work when the password entry box is active in GDM. This works fine with gnome-shell 43.0 and mutter 43.0. This is reproducible at will: just have two or more layouts available in GDM, hit 'enter' to select a user, and - now the password entry box is active - try super+space to switch layouts. It doesn't work. I've tried three cycles of downgrade to 43.0 -> reboot -> it works -> upgrade to 43.1 -> reboot -> it fails.

Layout switching works fine if you hit tab so the password entry box isn't active (though obviously this isn't ideal - it's quite natural to want/need to change the layout with the entry box active), and it works fine after logging in, in all the situations I tested. There may be other affected cases I didn't find (maybe other password entry fields?)