diff --git a/tox.ini b/tox.ini
index 5efc4c0..5326ba4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -36,7 +36,8 @@
   python setup.py test --coverage
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+commands =
+  sphinx-build -W -d doc/build/doctrees -b html doc/source/ doc/build/html
 
 [testenv:venv]
 commands = {posargs}