diff --git a/src/test/regress/mitmscripts/README.md b/src/test/regress/mitmscripts/README.md
index 805e2b5f86d..4b15d428cc4 100644
--- a/src/test/regress/mitmscripts/README.md
+++ b/src/test/regress/mitmscripts/README.md
@@ -25,7 +25,7 @@ Once you've installed it:
 
 ```bash
 $ cd src/test/regress
-$ pipenv --python 3.6
+$ pipenv --python 3.6 --python=`which python3.6`
 $ pipenv install  # there's already a Pipfile.lock in src/test/regress with packages
 $ pipenv shell  # this enters the virtual environment, putting mitmproxy onto $PATH
 ```