diff --git a/tox.ini b/tox.ini
index 4657203..537b2f2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -10,7 +10,7 @@ setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = python setup.py testr --slowest --testr-args='{posargs}'
+commands = ostestr {posargs}
 
 [testenv:pep8]
 commands = flake8