diff --git a/tox.ini b/tox.ini
index f0adbaf78eca987fa2f912b951bc2b58a36af673..930a49232a0322752c7d82c40b5b786e1a5c8ce1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -14,7 +14,7 @@ commands =
 [testenv:black]
 skip_install = true
 deps =
-  black
+  black==19.10b0
 commands =
   {envpython} -m black --check swh