diff --git a/tox.ini b/tox.ini
index fce4a4206..06de6f093 100644
--- a/tox.ini
+++ b/tox.ini
@@ -24,9 +24,11 @@ deps =
 
 [testenv:lint]
 commands =
+    black --check --diff src
     flake8 --statistics --count
     check-manifest
 deps =
+    black
     check-manifest
     flake8
 skip_install = true