diff --git a/reference/mongodb/architecture.xml b/reference/mongodb/architecture.xml
index c9c14b4491..f00ca0ebe5 100644
--- a/reference/mongodb/architecture.xml
+++ b/reference/mongodb/architecture.xml
@@ -142,7 +142,7 @@
    back into PHP land.
   </para>
 
-  <section>
+  <section xml:id="mongodb.persistence.serialization">
    <title>Serialisation to BSON</title>
 
    <section>
@@ -382,7 +382,7 @@ UpperClass implements MongoDB\BSON\Persistable {
    </section>
   </section>
 
-  <section>
+  <section xml:id="mongodb.persistence.deserialization">
    <title>Deserialization from BSON</title>
 
    <para>