diff --git a/sdks/python/apache_beam/runners/worker/bundle_processor.py b/sdks/python/apache_beam/runners/worker/bundle_processor.py
index 1b270b903729..97c318be18b3 100644
--- a/sdks/python/apache_beam/runners/worker/bundle_processor.py
+++ b/sdks/python/apache_beam/runners/worker/bundle_processor.py
@@ -610,3 +610,17 @@ def _create_combine_phase_operation(
           factory.state_sampler),
       transform_proto.unique_name,
       consumers)
+
+
+@BeamTransformFactory.register_urn(urns.FLATTEN_TRANSFORM, None)
+def create(factory, transform_id, transform_proto, unused_parameter, consumers):
+  return factory.augment_oldstyle_op(
+      operations.create_operation(
+          transform_proto.unique_name,
+          operation_specs.WorkerFlatten(
+              None,
+              [factory.get_only_output_coder(transform_proto)]),
+          factory.counter_factory,
+          factory.state_sampler),
+      transform_proto.unique_name,
+      consumers)