diff --git a/tox.ini b/tox.ini
index f331f68acc4..960e868fcea 100644
--- a/tox.ini
+++ b/tox.ini
@@ -31,7 +31,7 @@ passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 downloadcache = ~/cache/pip
 
 [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:common-constraints]
 install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}