diff --git a/.circleci/prepare.sh b/.circleci/prepare.sh
index dfd3aeef..035cdde7 100644
--- a/.circleci/prepare.sh
+++ b/.circleci/prepare.sh
@@ -1,6 +1,9 @@
+set -o errexit
+set -o xtrace
+
 $PYTHON --version
 $PYTHON -m pip --version
-$PYTHON -m pip install -q --user --ignore-installed --upgrade virtualenv
+$PYTHON -m pip install -q --user --ignore-installed virtualenv==20.0.23
 $PYTHON -m virtualenv -p $PYTHON venv
 venv/bin/python -m pip install -r requirements-dev.txt
 venv/bin/python -m pip freeze