diff --git a/tox.ini b/tox.ini
index 3e64a3a7..25155e9f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -63,7 +63,7 @@ commands =
     --output-file etc/sahara/sahara.conf.sample
 
 [testenv:releasenotes]
-commands = sphinx-build -a -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:pip-missing-reqs]
 # do not install test-requirements as that will pollute the virtualenv for