Pipenv always finds itself in a virtualenv

My Pipenv seems to always think it is in a virtual environment, even when it clearly is not:

$ cd /tmp/                                                      
/tmp $ mkdir hello                                                                       
/tmp $ cd hello/                                                                         
/t/hello $ pipenv install --python 3.8 --dev pylint                                      
Courtesy Notice: Pipenv found itself running within a virtual environment, so it will automatically use that environment, instead of creating its own for any project. You can set PIPENV_IGNORE_VIRTUALENVS=1 to force pipenv to ignore that environment and create its own instead. You can set PIPENV_VERBOSITY=-1 to suppress this warning.

How can I fix this?