diff --git a/setup.cfg b/setup.cfg
index ceef51f9..b4bf4652 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -43,6 +43,7 @@ storyboard.plugin.scheduler =
     token-cleaner = storyboard.plugin.token_cleaner.cleaner:TokenCleaner
 
 [build_sphinx]
+warning-is-error = 1
 source-dir = doc/source
 build-dir = doc/build
 all_files = 1
diff --git a/tox.ini b/tox.ini
index 1136957a..65c73142 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,10 +29,7 @@ deps = -r{toxinidir}/doc/requirements.txt
 commands =
     rm -rf doc/html doc/build
     rm -rf doc/source/apidoc doc/source/api
-    # NOTE(dhellmann): We cannot use -W with sphinx-build because the
-    # wsme.sphinxext registers a directive that is already registered
-    # and that warning causes the build to exit.
-    sphinx-build -b html doc/source doc/build/html
+    sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:cover]
 commands = python setup.py testr --coverage --testr-args='{posargs}'