diff --git a/tox.ini b/tox.ini
index 5d94e5c..f39c687 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,9 +35,9 @@ commands =
 basepython = python3
 skip_install = true
 deps =
-    black
+    black>=19.3b0
 commands =
-    black -l 78 -N src/
+    black --line-length 78 src/
 
 # Linters
 [testenv:flake8]