diff --git a/tox.ini b/tox.ini
index a5c3e6b..873aa12 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,41 +1,41 @@
 [tox]
 envlist=flake8,black
 
 [testenv]
 basepython = python3
 passenv = SPHINXOPTS JAVA_HOME
 
 [testenv:sphinx]
 extras =
   building
 deps =
   django < 3
   pifpaf
 setenv =
   SWHPKGDIR = {envsitepackagesdir}/swh
 commands =
   {envpython} -m pifpaf run postgresql -- make -C docs {posargs:html}
 
 [testenv:sphinx-dev]
 deps =
   django < 3
   -rrequirements-swh-dev.txt
   pifpaf
 setenv =
   SWHPKGDIR = {envsitepackagesdir}/swh
 commands =
   {envpython} -m pifpaf run postgresql -- make -C docs {posargs:html}
 
 [testenv:black]
 skip_install = true
 deps =
-  black
+  black==19.10b0
 commands =
   {envpython} -m black --check swh
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8