diff --git a/tox.ini b/tox.ini
index 0dc8677..338607e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,31 +1,32 @@
 [tox]
 envlist=check-manifest,flake8,mypy,py3
 
 [testenv]
+extras =
+  testing
 deps =
-  .[testing]
   pytest-cov
 commands =
   pytest --cov=swh --cov-branch {posargs}
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8
 
 [testenv:check-manifest]
 skip_install = true
 deps =
   check-manifest
 commands =
   {envpython} -m check_manifest {toxinidir}
 
 [testenv:mypy]
-skip_install = true
+extras =
+  testing
 deps =
-  .[testing]
   mypy
 commands =
   mypy swh