diff --git a/tox.ini b/tox.ini
index 1c3bb1b..5b33696 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,17 +1,17 @@
 [tox]
 envlist=flake8,mypy
 
 [testenv:flake8]
 skip_install = true
 deps =
   flake8
 commands =
   {envpython} -m flake8
 
 [testenv:mypy]
-skip_install = true
+extras =
+  testing
 deps =
-  .[testing]
   mypy
 commands =
   mypy swh