diff --git a/tox.ini b/tox.ini
index fcbf344..59f15d6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,40 +1,40 @@
 [tox]
 envlist=black,flake8,mypy,py3
 
 [testenv]
 extras =
   testing
 deps =
   # the dependency below is needed for now as a workaround for
   #   https://github.com/pypa/pip/issues/6239
   # TODO: remove when this issue is fixed
   swh.core[http] >= 0.0.61
   swh.storage[testing]
   swh.scheduler[testing] >= 0.5.0
   pytest-cov
 commands =
   pytest --cov={envsitepackagesdir}/swh/loader/git \
          {envsitepackagesdir}/swh/loader/git \
          --cov-branch {posargs}
 
 [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
 
 [testenv:mypy]
 extras =
   testing
 deps =
   mypy
 commands =
   mypy swh