diff --git a/tox.ini b/tox.ini
index ff34259c..c456915a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,6 +35,7 @@ deps =
   pytest-xdist
   flake8
   isort
+allowlist_externals = py.test
 commands = py.test {posargs}
 
 [testenv:flake8]