small sibling glue records help

[Anatoly Pugachev]

Hello.

Can someone explain me, what does mean:
18-Dec-2007 13:34:10.856 zone dom1.ru/IN: avgust.dom1.ru/NS 'ns.sub1.dom1.ru' has no SIBLING GLUE address records (A or AAAA)

Does that mean, that i should add A record for ns.sub1.dom1.ru into dom1.ru zone file?
I already have 

$ORIGIN dom1.ru
sub1    NS ns1.zone.ru.
        NS ns2.zone.ru.

Thanks.

-- 
Anatoly Pugachev