diff --git a/source/upgrade/v3.txt b/source/upgrade/v3.txt
index 9a623c89..7a88817a 100644
--- a/source/upgrade/v3.txt
+++ b/source/upgrade/v3.txt
@@ -111,12 +111,17 @@ Version 3.0 Breaking Changes
 - By default, the driver serializes ``Decimal128`` and ``decimal`` values as BSON
   ``Decimal128`` values. In previous versions of the driver, the driver serialized these
   values as BSON ``string`` values by default.
-  To serialize a ``decimal`` or ``Decimal128`` value as a string in v3.0, 
+  To serialize a ``decimal`` or ``Decimal128`` value as a string in v3.0,
   apply the ``[BsonRepresentation(BsonType.String)]`` attribute to the field.
   
   To learn more about specifying BSON types during serialization, see the
   :ref:`Custom Serialization <csharp-custom-serialization>` section of the POCOs page.
 
+- By default, the driver serializes ``DateTimeOffset`` values as BSON documents. In
+  previous versions of the driver, the driver serialized these values as BSON arrays by
+  default. To serialize a ``DateTimeOffset`` value as an array in v3.0, apply the
+  ``[BsonRepresentation(BsonType.Array)]`` attribute to the field.
+
 - The default JSON output mode is Relaxed Extended JSON, a string format based on the
   JSON standard that describes BSON documents. Relaxed Extended JSON emphasizes
   readability and interoperability at the expense of type preservation.
@@ -138,4 +143,4 @@ Version 3.0 Breaking Changes
      var json = document.ToJson(jsonWriterSettings);
 
 - The ``MongoClient`` constructor accepts only one ``Credential`` object instead of an
-  array.
\ No newline at end of file
+  array.