Bind Sync Unknown Command

Could anybody please, enlighten me on the following messages in my logs for Bind: sync 127.in-addr.arpa(unknown command): 2 Time(s) sync domain.com(unknown command): 2 Time(s) It's neither an error nor a warning. It's all up and running OK and I see no problems anywhere. How do I fix it what is it all about? I cannot seem to google anything on it. Many thanks in advance!