elixir_buildpack.config wasn't found in the app

[Awlexus]

I'm trying to use a custom elixir_buildpack.config. I placed it into the root directory as it is written in the readme and commit the file yet, when I push to heroku it can't seem to find the file

project $ tree -L 1
.
├── _build
├── config
├── deps
├── elixir_buildpack.config
├── lib
├── mix.exs
├── mix.lock
├── priv
├── Procfile
├── README.md
└── test

6 directories, 5 files
project $ git ls-files --error-unmatch elixir_buildpack.config
elixir_buildpack.config

Did I misunderstand something from the readme?

[Awlexus]

I cannot describe how stupid the error I made was