diff --git a/tests/test_sse.py b/tests/test_sse.py
index 6dfec61838..4317a8f322 100644
--- a/tests/test_sse.py
+++ b/tests/test_sse.py
@@ -6,6 +6,7 @@ import fastapi.routing
 import pytest
 from fastapi import APIRouter, FastAPI
 from fastapi.responses import EventSourceResponse
+from fastapi.routing import APIRoute
 from fastapi.sse import ServerSentEvent
 from fastapi.testclient import TestClient
 from pydantic import BaseModel
@@ -99,6 +100,20 @@ async def stream_events():
 app.include_router(router, prefix="/api")
 
 
+# Router with a typed SSE route to test stream_item_type propagation
+typed_router = APIRouter()
+
+
+@typed_router.get("/typed-events", response_class=EventSourceResponse)
+async def stream_typed_events() -> AsyncIterable[Item]:
+    for item in items:
+        yield item
+
+
+typed_app = FastAPI()
+typed_app.include_router(typed_router, prefix="/api")
+
+
 @pytest.fixture(name="client")
 def client_fixture():
     with TestClient(app) as c:
@@ -237,9 +252,7 @@ def test_raw_data_sent_without_json_encoding(client: TestClient):
     assert response.status_code == 200
     text = response.text
 
-    # raw_data should appear without JSON quotes
     assert "data: plain text without quotes\n" in text
-    # Not JSON-quoted
     assert 'data: "plain text without quotes"' not in text
 
     assert "event: html\n" in text
@@ -265,6 +278,23 @@ def test_sse_on_router_included_in_app(client: TestClient):
     assert len(data_lines) == 2
 
 
+def test_stream_item_type_propagated_through_include_router():
+    included_route = next(
+        r for r in typed_app.routes if getattr(r, "path", None) == "/api/typed-events"
+    )
+    assert isinstance(included_route, APIRoute)
+    assert included_route.stream_item_type is Item
+
+    with TestClient(typed_app) as client:
+        response = client.get("/api/typed-events")
+    assert response.status_code == 200
+    data_lines = [
+        line for line in response.text.strip().split("\n") if line.startswith("data: ")
+    ]
+    assert len(data_lines) == 3
+    assert '"name"' in data_lines[0]
+
+
 # Keepalive ping tests
 
 
@@ -274,8 +304,6 @@ keepalive_app = FastAPI()
 @keepalive_app.get("/slow-async", response_class=EventSourceResponse)
 async def slow_async_stream():
     yield {"n": 1}
-    # Sleep longer than the (monkeypatched) ping interval so a keepalive
-    # comment is emitted before the next item.
     await asyncio.sleep(0.3)
     yield {"n": 2}
 
@@ -293,7 +321,6 @@ def test_keepalive_ping_async(monkeypatch: pytest.MonkeyPatch):
         response = c.get("/slow-async")
     assert response.status_code == 200
     text = response.text
-    # The keepalive comment ": ping" should appear between the two data events
     assert ": ping\n" in text
     data_lines = [line for line in text.split("\n") if line.startswith("data: ")]
     assert len(data_lines) == 2
@@ -314,5 +341,4 @@ def test_no_keepalive_when_fast(client: TestClient):
     """No keepalive comment when items arrive quickly."""
     response = client.get("/items/stream")
     assert response.status_code == 200
-    # KEEPALIVE_COMMENT is ": ping\n\n".
     assert ": ping\n" not in response.text