diff --git a/tests/conftest.py b/tests/conftest.py
index 970c353..1ea3aa9 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -304,7 +304,7 @@ def serve_in_thread(server: Server):
 
 @pytest.fixture(scope="session")
 def server() -> typing.Iterator[TestServer]:
-    config = Config(app=app, lifespan="off", loop="asyncio")
+    config = Config(app=app, lifespan="off", loop="asyncio", http="h11")
     server = TestServer(config=config)
     yield from serve_in_thread(server)