diff --git a/gitlab/build.sh b/gitlab/build.sh
index a31680ac432fcd386a0574380223f061646a38d4..70152e77dbdeab56285273900623b3af034e4469 100755
--- 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 doc sphinx
+  run_cmd ./bin/sphinx-build -n -W doc sphinx
 fi
 
 if [ -z "${WHEEL_TAG}" ]; then