diff --git a/poky/documentation/ref-manual/ref-classes.xml b/poky/documentation/ref-manual/ref-classes.xml
index f8920d8..ab12373 100644
--- a/poky/documentation/ref-manual/ref-classes.xml
+++ b/poky/documentation/ref-manual/ref-classes.xml
@@ -1,6 +1,7 @@
 <!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
 [<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
+<!--SPDX-License-Identifier: CC-BY-2.0-UK-->
 
 <chapter id='ref-classes'>
 <title>Classes</title>