diff --git a/tox.ini b/tox.ini
index 4aaa22a..3da0118 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,32 +1,32 @@
 [tox]
 minversion = 1.4.2
 envlist = linters
 skipsdist = True
 
 [testenv]
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 
 [testenv:black]
 install_command = pip install {opts} {packages}
 commands =
   black -v -l79 {toxinidir}
 
 [testenv:linters]
 install_command = pip install {opts} {packages}
 commands =
-  black -v -l79 --check {toxinidir}
+  black -v -l79 --diff --check {toxinidir}
   flake8 {posargs}
   yamllint -s .
 
 [testenv:venv]
 commands = {posargs}
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
 
 show-source = True
 ignore = E123,E125,E402,W503
 max-line-length = 160
 builtins = _
 exclude = .git,.tox,tests/unit/compat/