slave bind skips delegation record in master zone

[kent at cpttm.org.mo]

Hi,

We have an NT4 DNS server hosting a zone for domain "foo" and
a Bind slave server for that zone. Everything is working fine
except that, if in the zone I add an NS record for bar.foo to
delegate it to a third DNS server like:

    bar.foo.   NS  c001.foo.

Then for some unknown reason the Bind server will silent
skip this record during zone transfer. That is, I checked the
zone file for "foo" on the Bind server and that record was
not there. Is there anything that I can check?

Thanks!