doveadm: Fatal: All your namespaces have a location setting

[Ben]

Hi,

I am trying to migrate mail from an old server and am receiving the 
following error :

doveadm(user at example.com): Fatal: All your namespaces have a location 
setting. Only namespaces with empty location settings are converted. 
(One namespace should default to mail_location setting)

I found an old thread 
(http://www.dovecot.org/list/dovecot/2012-September/068269.html) that 
referred to "location" being set.

However this is not the case with me, my config reads:
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     special_use = \Sent
   }
   mailbox Trash {
     special_use = \Trash
   }
   prefix =
}

My dsync conf looks as follows :
imapc_host = old-server.example.com
imapc_user = %u
imapc_features = rfc822.size
imapc_features = $imapc_features fetch-headers
mail_prefetch_count = 20
imapc_port = 993
imapc_ssl = imaps
imapc_ssl_verify = yes

The command I'm calling is:

sudo -u my_dovecot_user doveadm -c /etc/dovecot/dsync_config.conf -o 
mail_fsync=never backup -R -u user at example.com imapc: