diff --git a/tox.ini b/tox.ini
index be17f3d3..e0f3df17 100644
--- a/tox.ini
+++ b/tox.ini
@@ -59,4 +59,4 @@ deps =
 
 changedir = {toxinidir}
 commands =
-    sphinx-build -b html docs docs/build/html
+    sphinx-build -b html docs docs/build/html -W