diff --git a/tests/scripts/ci-util.sh b/tests/scripts/ci-util.sh
index 2ce3eb5e9b..6231bc980a 100755
--- a/tests/scripts/ci-util.sh
+++ b/tests/scripts/ci-util.sh
@@ -16,6 +16,7 @@
 
 # Exit immediately for non zero status
 set -e
+# Check unset variables
 set -u
 set -x