diff --git a/tox.ini b/tox.ini
index 247af9c..49dd952 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,3 +19,4 @@ commands=py.test --tb native {posargs:tests}
 [testenv:flake8]
 deps=flake8
 commands=flake8 {toxinidir}/cas.py
+skip_install = true