diff --git a/reference/mongodb/bson/persistable.xml b/reference/mongodb/bson/persistable.xml
index 28c8f4d3ca..dc0dd2b566 100644
--- a/reference/mongodb/bson/persistable.xml
+++ b/reference/mongodb/bson/persistable.xml
@@ -12,8 +12,26 @@
   <section xml:id="mongodb-bson-persistable.intro">
    &reftitle.intro;
    <para>
-
+    Classes may implement this interface to take advantage of automatic ODM
+    (object document mapping) behavior in the driver. During serialization, the
+    driver will inject a <property>__pclass</property> property containing the
+    PHP class name into the data returned by
+    <function>MongoDB\BSON\Serializable::bsonSerialize</function>. During
+    unserialization, the same <property>__pclass</property> property will then
+    be used to infer the PHP class (independent of any
+    <link linkend="mongodb.persistence.typemaps">type map</link> configuration)
+    to be constructed before
+    <function>MongoDB\BSON\Unserializable::bsonUnserialize</function> is
+    invoked. See <xref linkend="mongodb.persistence"/> for additional
+    information.
    </para>
+   <note>
+    <para>
+     Even if <function>MongoDB\BSON\Serializable::bsonSerialize</function> would
+     return a sequential array, injection of the <property>__pclass</property>
+     property will cause the object to be serialized as a BSON document.
+    </para>
+   </note>
   </section>
 <!-- }}} -->
 
diff --git a/reference/mongodb/bson/serializable/bsonserialize.xml b/reference/mongodb/bson/serializable/bsonserialize.xml
index d6d009f48b..6a02c07874 100644
--- a/reference/mongodb/bson/serializable/bsonserialize.xml
+++ b/reference/mongodb/bson/serializable/bsonserialize.xml
@@ -25,6 +25,14 @@
    document and sequential arrays (i.e. sequential, numeric indexes starting at
    <literal>0</literal>) will be serialized as a BSON array.
   </para>
+  <para>
+   Users are encouraged to include an <property>_id</property> property (e.g. a
+   <classname>MongoDB\BSON\ObjectID</classname> initialized in your constructor)
+   when returning data for a BSON root document; otherwise, the driver or
+   database will need to generate a
+   <classname>MongoDB\BSON\ObjectID</classname> when inserting or upserting the
+   document, respectively.
+  </para>
  </refsect1>
 
  <refsect1 role="parameters">
@@ -51,9 +59,16 @@
 
 class MyDocument implements MongoDB\BSON\Serializable
 {
+    private $id;
+
+    function __construct()
+    {
+        $this->id = new MongoDB\BSON\ObjectID;
+    }
+
     function bsonSerialize()
     {
-        return ['foo' => 'bar'];
+        return ['_id' => $this->id, 'foo' => 'bar'];
     }
 }
 
@@ -63,10 +78,10 @@ echo MongoDB\BSON\toJSON($bson), "\n";
 ?>
 ]]>
    </programlisting>
-   &example.outputs;
+   &example.outputs.similar;
    <screen>
 <![CDATA[
-{ "foo" : "bar" }
+{ "_id" : { "$oid" : "56cccdcada14d8755a58c591" }, "foo" : "bar" }
 ]]>
    </screen>
   </example>
diff --git a/reference/mongodb/bson/unserializable/bsonunserialize.xml b/reference/mongodb/bson/unserializable/bsonunserialize.xml
index 1e6feb4d37..fb87e693a6 100644
--- a/reference/mongodb/bson/unserializable/bsonunserialize.xml
+++ b/reference/mongodb/bson/unserializable/bsonunserialize.xml
@@ -17,6 +17,10 @@
    Called during unserialization of the object from BSON. The properties of the
    BSON array or document will be passed to the method as an <type>array</type>.
   </para>
+  <para>
+   Remember to check for an <property>_id</property> property when handling data
+   from a BSON document.
+  </para>
   <note>
    <para>
     This method acts as the