diff --git a/tox.ini b/tox.ini
index b1664259..7e36075e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -28,7 +28,7 @@ commands = flake8 {posargs}
 [testenv:py36-black]
 basepython = python3.6
 deps = black
-commands = black --check .
+commands = black --check --diff --color .
 
 [flake8]
 max_line_length = 88