diff --git a/etc/ci/manifest_changed.sh b/etc/ci/manifest_changed.sh
index b0eff206edf..9f3a6fd0b95 100755
--- a/etc/ci/manifest_changed.sh
+++ b/etc/ci/manifest_changed.sh
@@ -19,6 +19,7 @@ echo "About to update manifest."
 ./mach test-wpt --manifest-update --binary= SKIP_TESTS
 
 echo "Updated manifest; about to check if any changes were made to it."
+echo "If a diff is present, please run `./mach update-manifest` and commit the change."
 
 diff="$(git diff -- tests/*/MANIFEST.json)"
 echo "${diff}"