dig: REQUIRE(sock->parent == ((void *)0)) assertion failed in TCP mode

This happened for main, on OpenBSD:

https://gitlab.isc.org/isc-projects/bind9/-/jobs/1329045

I:dns64:checking non-mapped A via CNAME lookup is signed zone works with +dnssec (154)
netmgr/netmgr.c:963: REQUIRE(sock->parent == ((void *)0)) failed.
Abort trap (core dumped) 

D:dns64:Core was generated by `dig'.
D:dns64:Program terminated with signal SIGABRT, Aborted.
D:dns64:#0  thrkill () at /tmp/-:3
D:dns64:[Current thread is 1 (process 143154)]
D:dns64:#0  thrkill () at /tmp/-:3
D:dns64:#1  0x000009cac4e874be in _libc_abort () at /usr/src/lib/libc/stdlib/abort.c:51
D:dns64:#2  0x000009cacc5eef15 in isc_assertion_failed (file=<optimized out>, line=<optimized out>, type=<optimized out>, cond=<optimized out>) at assertions.c:47
D:dns64:#3  0x000009cacc5cd80c in isc__nmsocket_prep_destroy (sock=<optimized out>) at netmgr/netmgr.c:963
D:dns64:#4  0x000009cacc5d160f in isc_nm_tcpconnect (mgr=<optimized out>, local=0x9c844760df0 <localaddr>, peer=<optimized out>, cb=<optimized out>, cbarg=<optimized out>, timeout=<optimized out>, extrahandlesize=0) at netmgr/tcp.c:373
D:dns64:#5  0x000009cacc5d55e7 in isc_nm_tcpdnsconnect (mgr=0x9ca98339000, local=0x6, peer=0x0, cb=0x9c844757e00 <tcp_connected>, cbarg=0x9ca9835a008, timeout=0, extrahandlesize=0) at netmgr/tcpdns.c:850
D:dns64:#6  0x000009c8447561c4 in start_tcp (query=0x9ca9835a008) at dighost.c:2837
D:dns64:#7  0x000009c84475678c in onrun_callback (task=<optimized out>, event=0x0) at dighost.c:4179
D:dns64:#8  0x000009cacc610594 in dispatch (manager=0x9ca98350000, threadid=<optimized out>) at task.c:1152
D:dns64:#9  run (queuep=<optimized out>) at task.c:1344
D:dns64:#10 0x000009ca616abe21 in _rthread_start (v=<optimized out>) at /usr/src/lib/librthread/rthread.c:96
D:dns64:#11 0x000009cac4e4df48 in __tfork_thread () at /usr/src/lib/libc/arch/amd64/sys/tfork_thread.S:77
D:dns64:#12 0x0000000000000000 in ?? ()

I believe I have only seen this specific crash once so far, so this is not critical, but it also does not look OS-specific.