[Samba] objectGUID CNAME Record

[basti]

Hello,

i try
https://wiki.samba.org/index.php/Verifying_and_Creating_a_DC_DNS_Record

ldapvi '(invocationId=*)' --cross-ncs objectguid

I get objectGUID:: i55tljAenUWun3ISCvEXoQ==
When I do "samba-tool dns add dc1 _msdcs.foo i55tljAenUWun3ISCvEXoQ==
CNAME dc2.foo -Uadmin"
ERROR(runtime): uncaught exception - (8, 'WERR_NOMEM')
  File "/usr/lib/python2.7/dist-packages/samba/netcmd/__init__.py", line
175, in _run
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/samba/netcmd/dns.py", line
1077, in run
    0, server, zone, name, add_rec_buf, None)

When I try this without the == at the end of the guid it say "Record
added successfully"
Whats wrong here?