- command: expansions.update
     params:
       updates:
-      - key: activate_virtualenv
+      - key: python
         value: |
           # check if virtualenv is set up
-          if [ -d "${workdir}/venv" ]; then
+          if [ -d "${workdir}/venv" ] && [ -z $IN_VIRTUAL_ENV ]; then
             if [ "Windows_NT" = "$OS" ]; then
               # Need to quote the path on Windows to preserve the separator.
               . "${workdir}/venv/Scripts/activate" 2> /tmp/activate_error.log
@@ -1805,10 +1776,12 @@ pre:
               echo "Failed to activate virtualenv: $(cat /tmp/activate_error.log)"
             fi
             python=python
-          else
+            IN_VIRTUAL_ENV=1
+            echo "python set to $python"
+          elif [ -z $python ]; then
             python=${python|/opt/mongodbtoolchain/v2/bin/python2}
           fi
-          echo "python set to $(which python)"
+          $python \