diff --git a/tox.ini b/tox.ini
index 9bfe638c..9a7ab006 100644
--- a/tox.ini
+++ b/tox.ini
@@ -40,7 +40,7 @@ commands =
     # use `python setup.py check -m -r -s` instead.
     python setup.py check -m -s
     flake8 .
-    py.test tests
+    py.test tests {posargs}
 
 [flake8]
 exclude = .tox,*.egg,build,data