WARNING: Device "kbd" is Giant locked and may be deleted before FreeBSD 13.0.

Running FreeBSD CURRENT on a USB only platform with a customised kernel, I see this
message all the time I reboot or log console messages:

[...]
WARNING: Device "kbd" is Giant locked and may be deleted before FreeBSD 13.0.

Where does this message come from and what is causing the warning? I tried to identify
and eliminate this message, but it seems to be stuck with the USB device/keyboard
attached to the system.

Any hint?

Many thanks in advance,

oh