diff --git a/tox.ini b/tox.ini
index eeff471b..ce36efcb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,7 +8,7 @@ deps =
     pytest>=2.7.2  # see https://github.com/hynek/attrs/issues/14
     zope.interface
 commands =
-    coverage run --parallel -m pytest tests
+    coverage run --parallel -m pytest tests {posargs}
 
 
 [testenv:flake8]