diff --git a/tox.ini b/tox.ini
index 709f86e96..ec13335a3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,7 +17,7 @@ commands =
     {envpython} -c "import sys; print(sys.version)"
     {envpython} -c "import struct; print(struct.calcsize('P') * 8)"
     # run the test suite
-    py.test
+    py.test {posargs}
 
 [testenv:coveralls]
 passenv = TRAVIS TRAVIS_JOB_ID TRAVIS_BRANCH