diff --git a/src/confluent_kafka/schema_registry/avro.py b/src/confluent_kafka/schema_registry/avro.py
index 0a480e94c..fca75ab9c 100644
--- a/src/confluent_kafka/schema_registry/avro.py
+++ b/src/confluent_kafka/schema_registry/avro.py
@@ -121,6 +121,11 @@ class AvroSerializer(Serializer):
 
         See ``avro_producer.py`` in the examples directory for example usage.
 
+    Note:
+       Tuple notation can be used to determine which branch of an ambiguous union to take.
+
+       See `fastavro notation <https://fastavro.readthedocs.io/en/latest/writer.html#using-the-tuple-notation-to-specify-which-branch-of-a-union-to-take>`_
+
     Args:
         schema_registry_client (SchemaRegistryClient): Schema Registry client instance.