diff --git a/tox.ini b/tox.ini
index 32fc8756..b88e6dc7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,7 +6,7 @@ deps = -U
        -r{toxinidir}/tools/pip-requires
        -r{toxinidir}/tools/test-requires
 commands =
-  python ryu/tests/run_tests.py
+  python ryu/tests/run_tests.py '{posargs}'
 
 [testenv:pep8]
 commands =