diff --git a/tox.ini b/tox.ini
index e6f934c..5b2ca1e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,70 +17,53 @@ deps =
   pytest
   pytest-cov
   pytest-mock
-commands = 
-  pytest test/ --cov={toxinidir}/flat_tree/ --no-cov-on-fail {posargs}
+commands = pytest test/ --cov={toxinidir}/flat_tree/ --no-cov-on-fail {posargs}
 
 [testenv:lint]
 description = lint the source
 skipdist = True
-deps = 
-  flake8
-commands = 
-  flake8 {posargs} flat_tree/ test/
+deps = flake8
+commands = flake8 {posargs} flat_tree/ test/
 
 [testenv:sort]
 description = sort the source
 skipdist = True
-deps = 
-  isort
-commands = 
-  isort {posargs:-rc -c} -sp setup.cfg flat_tree/ test/
+deps = isort
+commands = isort {posargs:-rc -c} -sp setup.cfg flat_tree/ test/
 
 [testenv:format]
 description = format the source
 skipdist = True
 basepython = python3.6
-deps = 
-  black
-commands = 
-  black {posargs:--check} flat_tree/ test/
+deps = black
+commands = black {posargs:--check} flat_tree/ test/
 
 [testenv:type]
 description = type check the source
 basepython = python3.7
 skipdist = True
-deps = 
-  mypy
-commands = 
-  mypy flat_tree/ test/
+deps = mypy
+commands = mypy flat_tree/ test/
 
 [testenv:docs]
 description = build the documentation
-deps = 
-  sphinx
-  sphinx-autodoc-typehints >= 1.6.0, < 2.0
-commands = 
-  python -m setup build_sphinx
+extras = docs
+commands = python -m setup build_sphinx
 
 [testenv:changelog]
 description = draft the changelog
 skipdist = True
-deps = 
-  towncrier
-commands = 
-  towncrier --draft
+deps = towncrier
+commands = towncrier --draft
 
 [testenv:metadata-release]
 description = validate the package metadata
-deps =
-  twine
-commands =
-  twine check .tox/dist/*
+deps = twine
+commands = twine check {toxworkdir}/dist/*
 
 [testenv:release]
 description = make a release
-deps =
-  {[testenv:metadata-release]deps}
+deps = {[testenv:metadata-release]deps}
 commands =
     python -m setup sdist bdist_wheel
     twine upload {toxworkdir}/dist/*