[Dovecot] Virtual plugin - [SERVERBUG] BUG: Unknown internal error

/etc/dovecot/virtual/Inbox2/dovecot-virtual * -Trash -Trash/* -Deleted* -Junk* inthread x-references2 x-mailbox INBOX

Using php to connect o {host}virtual/Inbox2 gives me [SERVERBUG] BUG: Unknown internal error. If I connect to virtual/Allmail which has "all" instead of the inthread line it works.