diff --git a/tox.ini b/tox.ini
index 20f2f26..bc6e6cb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,30 +1,31 @@
 [tox]
 envlist=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
-  .[testing]
   pytest-cov
 commands =
   pytest --cov={envsitepackagesdir}/swh/loader/git \
          {envsitepackagesdir}/swh/loader/git \
          --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