diff --git a/event_model/__init__.py b/event_model/__init__.py
index 38a159a3..276ae0be 100644
--- a/event_model/__init__.py
+++ b/event_model/__init__.py
@@ -2056,14 +2056,14 @@ def compose_stream_datum(
 @dataclass
 class ComposeStreamResourceBundle:
     stream_resource_doc: StreamResource
-    compose_stream_data: List[ComposeStreamDatum]
+    compose_stream_datum: ComposeStreamDatum
 
     # iter for backwards compatibility
     def __iter__(self) -> Iterator:
         return iter(
             (
                 self.stream_resource_doc,
-                self.compose_stream_data,
+                self.compose_stream_datum,
             )
         )
 
diff --git a/event_model/tests/test_em.py b/event_model/tests/test_em.py
index 6fce1246..cc6962b4 100644
--- a/event_model/tests/test_em.py
+++ b/event_model/tests/test_em.py
@@ -119,7 +119,7 @@ def test_compose_stream_resource(tmp_path):
     )
     resource_doc, compose_stream_data = bundle
     assert bundle.stream_resource_doc is resource_doc
-    assert bundle.compose_stream_data is compose_stream_data
+    assert bundle.compose_stream_datum is compose_stream_data
     assert compose_stream_data[0] is not compose_stream_data[1]
     datum_doc_0, datum_doc_1 = (
         compose_stream_datum(datum_kwargs={})