diff --git a/.travis.yml b/.travis.yml
index 4a5ac7d..b107f12 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,4 +4,4 @@ install: pip install sphinx
 script: 
 - make doctest
 - make html
-- sphinx-build -E -c docs -b html docs docs/_build/html
+- sphinx-build -E -W -c docs -b html docs docs/_build/html