diff --git a/tox.ini b/tox.ini
index 494d5a3..c5e57be 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,6 +12,7 @@ deps = -r{toxinidir}/requirements.txt
 commands =
     find . -type f -name "*.pyc" -delete
     python setup.py testr --slowest --testr-args='{posargs}'
+whitelist_externals = find
 
 [testenv:pypy]
 deps = setuptools<3.2