nbd-client with TLS enabled cannot connect to nbdkit --tls=require

You can run these commands from the build directory to reproduce this problem:

$ nbdkit -U /tmp/sock -f -v --tls=require --tls-certificates tests/pki/ memory 1G
$ sudo nbd-client -u /tmp/sock -x -cacertfile tests/pki/ca-cert.pem -certfile tests/pki/client-cert.pem -keyfile tests/pki/client-key.pem -n /dev/nbd0

Fails with this error on the client side:

Warning: the oldstyle protocol is no longer supported.
This method now uses the newstyle protocol with a default export
Negotiation: ..E: received invalid negotiation magic 10641517674210066432 (expected 1100100111001001)

(Note I think this could be a bug in nbd-client)