diff --git a/tox.ini b/tox.ini
index eb48ca09..763892a0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,29 +1,30 @@
 [tox]
 envlist=flake8,mypy,py3
 
 [testenv]
+extras =
+  testing
 deps =
-  .[testing]
   pytest-cov
 commands =
   pytest \
     !slow: --hypothesis-profile=fast \
     slow:  --hypothesis-profile=slow \
          --cov={envsitepackagesdir}/swh/storage \
          {envsitepackagesdir}/swh/storage \
          --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