diff --git a/tox.ini b/tox.ini
index 74f6f956b..3fdb14590 100644
--- a/tox.ini
+++ b/tox.ini
@@ -54,7 +54,7 @@ basepython = python3.6
 commands = pytest {posargs}
 
 [testenv:cover]
-commands = python setup.py test --coverage --testr-args='{posargs}'
+commands = python setup.py test --coverage --testr-args={posargs}
 
 [testenv:docs]
 commands = python setup.py build_sphinx