diff --git a/tox.ini b/tox.ini
index 0d66a847..829a9af0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,7 @@ deps =
     black
 commands =
     {[testenv]commands}
-    black --check pungi pungi_utils setup.py tests --exclude tests/_composes
+    black --check --diff pungi pungi_utils setup.py tests --exclude tests/_composes
 
 [flake8]
 exclude = doc/*,*.pyc,*.py~,*.in,*.spec,*.sh,*.rst