diff --git a/tox.ini b/tox.ini
index e4d3db4bc..8ebbf4954 100644
--- a/tox.ini
+++ b/tox.ini
@@ -58,7 +58,7 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -b html doc/source doc/build/html
+commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:releasenotes]
 basepython = python3