diff --git a/src/openai/lib/streaming/responses/_responses.py b/src/openai/lib/streaming/responses/_responses.py
index 6975a9260d..513ca5dbb5 100644
--- a/src/openai/lib/streaming/responses/_responses.py
+++ b/src/openai/lib/streaming/responses/_responses.py
@@ -328,18 +328,20 @@ def accumulate_event(self, event: RawResponseStreamEvent) -> ParsedResponseSnaps
             return self._create_initial_response(event)
 
         if event.type == "response.output_item.added":
-            if event.item.type == "function_call":
+            item = event.item
+            if item is None:
+                return snapshot
+
+            if item.type == "function_call":
                 snapshot.output.append(
-                    construct_type_unchecked(
-                        type_=cast(Any, ParsedResponseFunctionToolCall), value=event.item.to_dict()
-                    )
+                    construct_type_unchecked(type_=cast(Any, ParsedResponseFunctionToolCall), value=item.to_dict())
                 )
-            elif event.item.type == "message":
+            elif item.type == "message":
                 snapshot.output.append(
-                    construct_type_unchecked(type_=cast(Any, ParsedResponseOutputMessage), value=event.item.to_dict())
+                    construct_type_unchecked(type_=cast(Any, ParsedResponseOutputMessage), value=item.to_dict())
                 )
             else:
-                snapshot.output.append(event.item)
+                snapshot.output.append(item)
         elif event.type == "response.content_part.added":
             output = snapshot.output[event.output_index]
             if output.type == "message":
diff --git a/tests/lib/responses/test_responses.py b/tests/lib/responses/test_responses.py
index 8e5f16df95..5bba1fe2c1 100644
--- a/tests/lib/responses/test_responses.py
+++ b/tests/lib/responses/test_responses.py
@@ -8,6 +8,8 @@
 
 from openai import OpenAI, AsyncOpenAI
 from openai._utils import assert_signatures_in_sync
+from openai.types.responses import Response, ResponseCreatedEvent, ResponseOutputItemAddedEvent
+from openai.lib.streaming.responses._responses import ResponseStreamState
 
 from ...conftest import base_url
 from ..snapshots import make_snapshot_request
@@ -61,3 +63,35 @@ def test_parse_method_definition_in_sync(sync: bool, client: OpenAI, async_clien
         checking_client.responses.parse,
         exclude_params={"tools"},
     )
+
+
+def test_response_stream_ignores_null_output_item_added() -> None:
+    response = Response.model_construct(
+        id="resp_123",
+        created_at=0.0,
+        model="gpt-4o",
+        object="response",
+        output=[],
+        parallel_tool_calls=True,
+        tool_choice="auto",
+        tools=[],
+    )
+    state = ResponseStreamState(input_tools=[], text_format=str)
+
+    state.handle_event(
+        ResponseCreatedEvent.model_construct(
+            type="response.created",
+            sequence_number=0,
+            response=response,
+        )
+    )
+    events = state.handle_event(
+        ResponseOutputItemAddedEvent.model_construct(
+            type="response.output_item.added",
+            sequence_number=1,
+            output_index=0,
+            item=None,
+        )
+    )
+
+    assert [event.type for event in events] == ["response.output_item.added"]