dovecot - May 2016 - Panic: file doveadm-mail.c: line 417 (doveadm_mail_single_user): assertion failed: (cctx->username != NULL)

Hello everyone!

So, I'm trying to move away from a few older servers into new ones but I
can't get dsync to work this time (the 2013 migration went perfectly). This
is what I get:

root at dovecot:/# dsync sync -u user at domain.org.br tcp:XXXX:12345
Panic: file doveadm-mail.c: line 417 (doveadm_mail_single_user): assertion
failed: (cctx->username != NULL)
Error: Raw backtrace: /usr/lib/dovecot/libdovecot.so.0(+0x85dee)
[0x7f500d3cddee] -> /usr/lib/dovecot/libdovecot.so.0(+0x85e68)
[0x7f500d3cde68] -> /usr/lib/dovecot/libdovecot.so.0(i_fatal+0)
[0x7f500d3725be] -> dsync(+0x28d50) [0x55dcb11bad50] -> dsync(+0x28ded)
[0x55dcb11baded] -> dsync(doveadm_mail_try_run+0x219) [0x55dcb11bb779] ->
dsync(main+0x441) [0x55dcb11aba91] ->
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f500cfbeb45] ->
dsync(+0x19c06) [0x55dcb11abc06]
Aborted (core dumped)
root at dovecot:/#

doveconf -N is here: http://pastebin.ca/3594094

doveadm user '*" will list all the users correctly

doveadm user user at domain.org.br will show all the user info correctly.

Thank you very much!

Best,
Daniel Colchete