diff --git a/mkosi.clean b/mkosi.clean
index bcd1ae42c89..dac2f1bf421 100755
--- a/mkosi.clean
+++ b/mkosi.clean
@@ -1,4 +1,6 @@
 #!/bin/bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
 set -e
 set -o nounset