sndio install: pw: user '_sndio' disappeared during update

[Gary Aitken]

# pkg install sndio
...
New packages to be INSTALLED:
         sndio: 1.7.0
...
Proceed with this action? [y/N]: y
[1/1] Installing sndio-1.7.0...
===> Creating groups.
Using existing group '_sndio'.
===> Creating users
Creating user '_sndio' with uid '702'.
pw: user '_sndio' disappeared during update
pkg: PRE-INSTALL script failed

Anyone know what this is about?

Thanks,

Gary