Bind9 does not re-read zone files on -HUP

[John Lange]

I have a bind9 server which uses the INCLUDE directive to load a "common"
portion of a Zone file (the header including serial number and several A
host records), and then 2 separate portions of the zone file, one for
internal host lookups and one for external lookups.

I've noticed that when I make changes to the common portion of the zone file
and then -HUP named, it does not re-read the zone file(s). (and yes, I made
sure to change the serial number).

Apologies if this is already a known thing.

John Lange