diff --git a/tox.ini b/tox.ini
index 1a571e1..fb3c99d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,26 +1,27 @@
 [tox]
 envlist=flake8,mypy,py3
 
 [testenv]
+extras =
+  testing
 deps =
-  .[testing]
   pytest-cov
 commands =
   pytest --cov={envsitepackagesdir}/swh/loader/mercurial \
          {envsitepackagesdir}/swh/loader/mercurial \
          --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8
 
 [testenv:mypy]
-skip_install = true
+extras =
+  testing
 deps =
-  .[testing]
   mypy
 commands =
   mypy swh