[yocto] Help with DISTRO settings

[Edward Wingate]

This is in my layer's conf/distro/mydistro.conf file:

    require conf/distro/poky.conf
    DISTRO = "mydistro"
    DISTRO_NAME = "MyDistro"

These variables took effect before, but now bitbake is reverting back
to DISTRO="poky" and DISTRO_NAME = "Poky (Yocto Project Reference
Distro)" (used for /etc/issue) for some reason.

How can I determine what is reverting it?  I don't know what I might
have changed to make it do this. Thank you.