diff --git a/doc/doap.xml b/doc/doap.xml
index b5dd54d5c..234a5fc22 100644
--- a/doc/doap.xml
+++ b/doc/doap.xml
@@ -51,6 +51,7 @@
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc6120"/>
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc6121"/>
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc6122"/>
+    <implements rdf:resource="https://www.rfc-editor.org/info/rfc6331"/>
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc6455"/>
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc7233"/>
     <implements rdf:resource="https://www.rfc-editor.org/info/rfc7301"/>