diff --git a/tox.ini b/tox.ini
index ef144e2e..9addc499 100644
--- a/tox.ini
+++ b/tox.ini
@@ -69,7 +69,8 @@ commands =
 commands = {posargs}
 
 [testenv:docs]
-commands = python setup.py build_sphinx
+commands =
+  sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:pdf-docs]
 envdir = {toxworkdir}/docs