pipenv: "python-dotenv" reappearing after every pipenv install

Question

every time i run pipenv install it will reinstall python-dotenv. I was using python-dotenv for a while, but I want to use django-dotenv instead.

So, I want to remove it, hence i execute:

$ pipenv uninstall python-dotenv
$ pipenv graph | grep python-dotenv    // shows no output, so it seems to be removed

Now, I realize that it's still in the "Pipfile.lock" and when i run pipenv sync or pipenv install it will install "python-dotenv" again.

So I remove the python-dotenv block from the Pipfile.lock manually. I then run

$ pipenv lock
$ cat Pipfile.lock | grep python-dotenv
        "python-dotenv": {

which shows that it has added it again to the lockfile. It's not in my pipfile and there is no transitive dependency to it - according to the pipenv graph

if i now run pipenv install or pipenv sync it will install it again.

I can't figure out why python-dotenv keeps reappearing and how to remove it permanently. Can anyone help me with this issue?