[Dovecot] Setting mail location in SQL?

[Marc Perkel]

Trying to figure out the syntax to set a mail_location for SQL. This 
doesn't work:

userdb {
  driver = sql
  args = /etc/dovecot/master-combined-sql.conf
  override_fields = 
mail_location=maildir:/fakedir/%d/%n:INBOX=/fakedir:LAYOUT=fs
}
Does anyone know the proper syntax?
Thanks in advance