unexpected RCODE (SERVFAIL)

[MBernha at bart.gov]

I'm running 9.3.3.

Jan 18 10:00:46 dns-server named[27452]: unexpected RCODE (SERVFAIL)
resolving '170.252.127.65.in-addr.arpa/PTR/IN': w.x.y.z#53
Jan 18 10:00:59 dns-server named[27452]: unexpected RCODE (SERVFAIL)
resolving '244.49.58.82.in-addr.arpa/PTR/IN': w.x.y.z#53
Jan 18 10:01:26 dns-server named[27452]: unexpected RCODE (SERVFAIL)
resolving '101.200.213.64.in-addr.arpa/PTR/IN': w.x.y.z#53

I understand what these messages mean, but since this server is set up for
forward-only, I don't care about them. How do I tell named not to log
these?