fontconfig-config keeps reinstating files

Every time the fontconfig-config package is updated it is installing a new copy of all the files under /etc/fonts/conf.d. This means that it keeps installing /etc/fonts/conf.d/70-no-bitmaps.conf, which i have deleted, which then overrides the 70-yes-bitmaps.conf file which I have created.

Surely this kind of file should not be created on an upgrade? I would have thought this would be considered a configuration file and only created on the first install.

Am I missing something? I am pretty sure this didn't use to happen.