diff --git a/inbox/cs-2021.xml b/inbox/cs-2021.xml
index 10fa77a9..618625d3 100644
--- a/inbox/cs-2021.xml
+++ b/inbox/cs-2021.xml
@@ -62,6 +62,14 @@
       <email>georg@op-co.de</email>
       <jid>georg@yax.im</jid>
     </author>
+    <revision>
+      <version>0.0.1</version>
+      <date>2020-09-02</date>
+      <initials>gl</initials>
+      <remark>
+        <p>First draft based on XEP-0423.</p>
+      </remark>
+    </revision>
   </header>
   <section1 topic='Introduction' anchor='intro'>
     <p>