dovecot - Jun 2016 - error using default_fields in passwd-file

I'm trying to put virtual user mail in:
/var/vmail/<domain>/<user-local-part>

 

I tried setting the home field in the userdb to /var/vmail/%d/%n

But apparently variable expansion doesn't happen in the userdb because the
Dovecot LDA created the literal directory /var/vmail/%d/%n/Maildir

 

So then I tried  to use default_fields as shown here:
http://wiki2.dovecot.org/AuthDatabase/PasswdFile

 

So my config is:

 

userdb {

  driver = passwd-file

  args = username_format=%n /etc/dovecot/auth.d/%d/passwd

  default_fields = home=/var/vmail/%d/%u

}

 

But when I reload doveadm I get:

 

doveconf: Fatal: Error in configuration file /etc/dovecot/local.conf line
87: Unknown setting: default_fields

 

I tried override_fields:

 

userdb {

  driver = passwd-file

  args = username_format=%n /etc/dovecot/auth.d/%d/passwd

  override_fields = home=/var/vmail/%d/%u

}

 

And I get the same type of error:

 

doveconf: Fatal: Error in configuration file /etc/dovecot/local.conf line
87: Unknown setting: override_fields

 

What gives?

 

Michael