diff --git a/tox.ini b/tox.ini
index 3dbe78e55666..1f1ca101e37d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -210,7 +210,7 @@ deps = -r{toxinidir}/test-requirements.txt
 commands = bandit -c bandit.yaml -r nova -n 5 -ll
 
 [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
 
 [flake8]
 # E125 is deliberately excluded. See https://github.com/jcrocholl/pep8/issues/126