diff --git a/gitlab/build.sh b/gitlab/build.sh
index a1c2fe1b79432e17ccac989da788483de1644968..6d45957122a54ece216884168058bb796aed9c73 100644
--- a/gitlab/build.sh
+++ b/gitlab/build.sh
@@ -10,7 +10,7 @@ if [ -x ./bin/bob_dbmanage.py ]; then
 fi
 
 if [ -d ./doc ]; then
-  run_cmd ./bin/sphinx-build -n doc sphinx
+  run_cmd ./bin/sphinx-build -W doc sphinx
 fi
 
 if [ -z "${WHEEL_TAG}" ]; then