diff --git a/tox.ini b/tox.ini
index 6b326904..2fbc1fba 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,7 @@ commands =
 commands = pylint os_doc_tools cleanup
 
 [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:venv]
 commands = {posargs}