I removed the telegram/py.typed I added before to overcome this issue and uninstalled the previous python-telegram-bot version. After installing the pep561 branch, the same error occurs again. This doesn't solve the problem for me.

I don't know if it's worth mentioning: I'm using poetry as a package manager.

Okay … I'll look into it :)

py.typed was just in the wrong dir. I've checked that python setup.py sdist bdist_wheel includes telegram/py.typed both in the wheel and in the .tar.gz and installing from this branch also worked. @letmejustputthishere could you double check on your end by installing from this branch?

It works like a charm, thanks a lot!