diff --git a/contrib/run-unittests.sh b/contrib/run-unittests.sh
index b9d88240..dbba3a9e 100755
--- a/contrib/run-unittests.sh
+++ b/contrib/run-unittests.sh
@@ -34,7 +34,7 @@ postgres_image="postgres:9.5.17"
 test_container_name="mbs-test"
 db_container_name="mbs-test-db"
 source_dir="$(realpath "$(dirname "$0")/..")"
-volume_mount="${source_dir}:/src:Z"
+volume_mount="${source_dir}:/src:z"
 db_name=mbstest
 db_password=mbstest
 pgdb_uri="postgresql+psycopg2://postgres:${db_password}@db/${db_name}"