TCP client not being identified in log message

I was trying to match expected log messages in a system test (!5616 (merged)) and switching from UDP to TCP to force a SERVFAIL rather than timeout response resulted in <unknown> for the client being logged instead of IP address and port.

06-Dec-2021 16:26:06.430 DNS format error from 10.53.0.8#5300 resolving tcpalso.no-questions/A for <unknown>: empty question section, accepting it anyway as TC=1

The string I was expecting to match against was

resolving tcpalso.no-questions/A for 10.53.0.5#[0-9]*: empty question section, accepting it anyway as TC=1

I haven't checked 9.16 yet.