diff --git a/tox.ini b/tox.ini
index fe3485d5..53a8bd74 100644
--- a/tox.ini
+++ b/tox.ini
@@ -27,9 +27,7 @@ basepython = python2
 commands = {posargs}
 
 [testenv:docs]
-# NOTE: -W is not added since ocata/ptl.rst throws a warning about duplicate
-# IDs.
-commands = sphinx-build -b html -d doc/build/doctrees doc/source doc/build/html
+commands = sphinx-build -v -W -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:ci-checks]
 commands = ci-check-all-candidate-files