diff --git a/tox.ini b/tox.ini
index 7191cb14..fd07aa5b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,6 +11,7 @@ deps =
     {[testenv]deps}
 [testenv:cov]
 deps =
+    coverage
     {[testenv]deps}
 commands =
     coverage run --source jedi -m py.test