Milter-greylist: cannot read dumpfile

OS type and version Debian 11
Webmin version 2.101
Virtualmin version 7.8.2
Related packages postgrey 1.36
postfix 3.5.18

Postfix is active and running.
Postgrey is active and running.
Greylisting seems to be working.

However, file greylist.db is not created.
An error is logged to journalctl:

milter-greylist[397]: cannot read dumpfile "/var/lib/milter-greylist/greylist.db"
milter-greylist[397]: starting with an empty greylist

Hmm. Nobody has any ideas?

Does this happen more than once? That’s a normal start the first time.