nsd users - Jul 2003 - nsd replies with NOTIMP when receiving a NOTIFY?

The primary (a BIND9) of a zone ("test.") served (as a secondary) by
our nsd complains:

Jul 16 17:52:45.796 notify: debug 3: zone test/IN: notify response from
192.134.7.251#53: NOTIMP

After all, nsd implements the NOTIFY, it logs them and SEC parses the
log file to run "nsdc update". Isn't it an error to send a NOTIMP?

nsd 1.2.1