Ash Framework B4: `mix ash.gen.domain Tunez.Music` fails (page 6)

Running that command results in:

% mix ash.gen.domain Tunez.Music

Issues:

* lib/tunez/music.ex: Igniter would have produced invalid syntax.

This is almost certainly a bug in Igniter, or in the implementation
of the task/function you are using.

** (UndefinedFunctionError) function Ash.Domain.default_extensions/0 is undefined (module Ash.Domain is not available)
    (rewrite 1.1.2) lib/rewrite/source.ex:953: Rewrite.Source.format!/2
    (igniter 0.5.38) lib/igniter.ex:1430: anonymous fn/2 in Igniter.format/3
    (igniter 0.5.38) lib/igniter.ex:1513: Igniter.with_evaled_configs/2
    (igniter 0.5.38) lib/igniter.ex:1428: anonymous fn/5 in Igniter.format/3
    (elixir 1.18.3) lib/enum.ex:4515: anonymous fn/3 in Enum.reduce/3
    (elixir 1.18.3) lib/enum.ex:4968: Enumerable.List.reduce/3
    (elixir 1.18.3) lib/enum.ex:4515: Enum.reduce/3
    (igniter 0.5.38) lib/igniter.ex:1421: Igniter.format/3

I was following all instructions up until that point.

Elixir 1.18.3-opt-27, Erlang 27.3