"dig +nssearch" does not exit until interrupted in BIND 9.18+

On my laptop, I am consistently observing the following behavior:

$ dig +nssearch isc.org.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 51.75.79.143 in 19 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 199.6.1.52 in 23 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 2001:500:60:d::52 in 23 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 2001:4f8:1:f::73 in 156 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 149.20.1.73 in 166 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 2001:41d0:701:1100::2c92 in 166 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 199.254.63.254 in 169 ms.
SOA ns-int.isc.org. hostmaster.isc.org. 2022020916 7200 3600 24796800 3600 from server 2001:500:2c::254 in 246 ms.
<...hangs...>
^C$

AFAICT, this issue is not specific to my local environment, to the address family used, etc.