diff --git a/tox.ini b/tox.ini
index 8ef166c4..da1bc2a3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,6 +19,7 @@ exclude =
 [testenv]
 usedevelop = true
 sitepackages = true
+whitelist_externals = flake8
 deps = -r{toxinidir}/test-requirements.txt
 commands =
     py.test -v \