diff --git a/docs/contributing.rst b/docs/contributing.rst
index 9ceb0fbdd..633af19c6 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -317,7 +317,9 @@ Steps:
 3. Run ``./pep8.travis.sh`` to do a cursory check of your code style.
    Fix any errors.
 4. Run ``tox -e lint`` to check for pylint errors. Fix any errors.
-5. Run ``tox`` to run the entire test suite including coverage. Fix any errors.
+5. Run ``tox --skip-missing-interpreters`` to run the entire test suite
+   including coverage. The ``--skip-missing-interpreters`` argument ignores
+   missing versions of Python needed for running the tests. Fix any errors.
 6. If your code touches communication with an ACME server/Boulder, you
    should run the integration tests, see `integration`_. See `Known Issues`_
    for some common failures that have nothing to do with your code.