diff --git a/tox.ini b/tox.ini
index 7502fa1..5064487 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,6 +26,7 @@ commands =
 deps =
     {[testenv:notpy33]deps}
     {[testenv:all]deps}
+    argparse
     unittest2
 
 [testenv:pypy]