diff --git a/docs/reference/api/ModemManager-docs.xml b/docs/reference/api/ModemManager-docs.xml
index 2ad007b8..b25e8445 100644
--- a/docs/reference/api/ModemManager-docs.xml
+++ b/docs/reference/api/ModemManager-docs.xml
@@ -154,4 +154,8 @@
     <title>Index of new symbols in 1.18</title>
     <xi:include href="xml/api-index-1.18.xml"></xi:include>
   </chapter>
+  <chapter id="api-index-1-20" role="1.20">
+    <title>Index of new symbols in 1.20</title>
+    <xi:include href="xml/api-index-1.20.xml"></xi:include>
+  </chapter>
 </book>