RE: Iteration failure on passwd-file when listing all users?

I'm trying to get a list of all dovecot users, on a simple test setup on my local network (which "works", in that I can get IMAP mails from dovecot):

passdb { driver = passwd-file args = /var/mail/vhosts/%d/shadow } userdb { driver = passwd-file args = /var/mail/vhosts/%d/passwd }

The command 'doveadm user -u foo@example.com' correctly shows that user. However, any attempt to wildcard the user fails:

# doveadm user -u *@example.com Error: auth-master: userdb list: User listing returned failure Fatal: user listing failed

The log file shows

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