diff --git a/src/openai/lib/streaming/responses/_responses.py b/src/openai/lib/streaming/responses/_responses.py
index da4c00f845..23af68bb3c 100644
--- a/src/openai/lib/streaming/responses/_responses.py
+++ b/src/openai/lib/streaming/responses/_responses.py
@@ -394,6 +394,8 @@ def _create_initial_response(self, event: RawResponseStreamEvent) -> ParsedRespo
             raise RuntimeError(f"Expected to have received `response.created` before `{event.type}`")
 
         snapshot = construct_type_unchecked(type_=ParsedResponseSnapshot, value=event.response.to_dict())
+        if getattr(snapshot, "output", None) is None:
+            snapshot.output = []
         # Stream indexes can have gaps when a provider emits an empty added event.
-        self._output_items = dict(enumerate(snapshot.output or []))
+        self._output_items = dict(enumerate(snapshot.output))
         return snapshot
diff --git a/tests/lib/responses/test_null_output.py b/tests/lib/responses/test_null_output.py
index 4c782de03a..8113564e37 100644
--- a/tests/lib/responses/test_null_output.py
+++ b/tests/lib/responses/test_null_output.py
@@ -15,9 +15,12 @@ class Answer(BaseModel):
 
 
 @pytest.mark.parametrize("sync", [True, False], ids=["sync", "async"])
+@pytest.mark.parametrize("initial_output", ["null", "missing", "empty"])
 @pytest.mark.parametrize("terminal_output", ["null", "missing", "empty", "present"])
 @pytest.mark.parametrize("has_items", [True, False], ids=["with-items", "without-items"])
-async def test_stream_recovers_finalized_output(sync: bool, terminal_output: str, has_items: bool) -> None:
+async def test_stream_recovers_finalized_output(
+    sync: bool, initial_output: str, terminal_output: str, has_items: bool
+) -> None:
     items: list[dict[str, object]] = (
         [
             {
@@ -54,7 +57,9 @@ async def test_stream_recovers_finalized_output(sync: bool, terminal_output: str
         if has_items
         else []
     )
-    response: dict[str, object] = {"id": "resp_test", "status": "in_progress", "output": []}
+    response: dict[str, object] = {"id": "resp_test", "status": "in_progress"}
+    if initial_output != "missing":
+        response["output"] = None if initial_output == "null" else []
     events: list[dict[str, object]] = [{"type": "response.created", "response": response}]
     for index, item in enumerate(items):
         added = {**item, "status": "in_progress"}