Add sphinx-docstring-typing
diff --git a/tox.ini b/tox.ini
index ffaef94..ce942f1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,6 +35,7 @@
 deps =
   {[testenv]deps}
   sphinx
+  -r{toxinidir}/docs/requirements-docs.txt
 commands = make -C docs html
 
 [testenv:lint]