mirror on/off reconfig incomplete

If I switch mirror on or off using rndc reconfig, named does not reconfigure the mirror zone completely.

Test 1

I start with named.conf containing only the mirror example from the ARM (no other zones, no options section).

I dig . soa @::1 and I get flags: qr rd ra ad; as expected

I edit named.conf to comment out the mirror yes line and run rndc reconfig.

When I dig again I get the same flags. I expected AA=1 AD=0.

I restart named and dig again, and I get flags: qr aa rd ra; as expected.

Test 2

Having started named with mirroring disabled/commented out (the state at the end of Test 1), I uncomment the mirror line and run rndc reconfig to enable it again.

When I dig again I get flags: qr rd ra; which has AA=0 as expected but not AD=1.

Test 3

I stop named and add the following to named.conf.

options {
        recursion no;
        allow-query-cache { localhost; };
        allow-query { localhost; };
};

I start named again (mirroring is enabled). When I dig I get flags: qr rd ad; as expected.

I edit named.conf to turn off mirroring, and remove the allow-query-cache option, so the configuration becomes auth-only. I run rndc reconfig.

When I dig I get REFUSED. I expected an AA=1 answer. After I restart named I get the answer as expected.