Warning "Obsolete name arg "password-store" to constructor auth-source-backend"

[Alex Branham]

Hi all -

I'm seeing the following warning when byte compiling
auth-password-store[1] on Emacs 26:

 auth-password-store.el:82:1:Warning: Obsolete name arg "password-store" to
      constructor auth-source-backend

Does anyone have any idea what this could mean or how to fix it? I
raised this in a github issue[2] and the package's authors seem as
perplexed as I am.

Any advice is appreciated!
Alex

Footnotes:
[1]  https://github.com/DamienCassou/auth-password-store

[2]  https://github.com/DamienCassou/auth-password-store/issues/54