diff --git a/jupyter_ydoc/ynotebook.py b/jupyter_ydoc/ynotebook.py
index 47ae466..b4bd0ad 100644
--- a/jupyter_ydoc/ynotebook.py
+++ b/jupyter_ydoc/ynotebook.py
@@ -221,8 +221,8 @@ def get(self) -> Dict:
         return dict(
             cells=cells,
             metadata=meta.get("metadata", {}),
-            nbformat=int(meta.get("nbformat", 0)),
-            nbformat_minor=int(meta.get("nbformat_minor", 0)),
+            nbformat=int(meta.get("nbformat", NBFORMAT_MAJOR_VERSION)),
+            nbformat_minor=int(meta.get("nbformat_minor", NBFORMAT_MINOR_VERSION)),
         )
 
     def set(self, value: Dict) -> None:
diff --git a/pyproject.toml b/pyproject.toml
index 7923d5c..fa89f80 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,7 +31,7 @@ test = [
     "pytest",
     "pytest-asyncio",
     "websockets >=10.0",
-    "ypy-websocket >=0.8.3,<0.9.0",
+    "ypy-websocket >=0.8.3,<0.13.0",
 ]
 docs = [
     "sphinx",
diff --git a/tests/conftest.py b/tests/conftest.py
index ed1740f..7d56267 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -32,9 +32,13 @@ async def yws_server(request):
         kwargs = request.param
     except Exception:
         kwargs = {}
+
     websocket_server = WebsocketServer(**kwargs)
-    async with serve(websocket_server.serve, "localhost", 1234):
-        yield websocket_server
+    try:
+        async with websocket_server, serve(websocket_server.serve, "localhost", 1234):
+            yield websocket_server
+    except Exception:
+        pass
 
 
 @pytest.fixture
diff --git a/tests/test_ypy_yjs.py b/tests/test_ypy_yjs.py
index 5ba157b..744ae16 100644
--- a/tests/test_ypy_yjs.py
+++ b/tests/test_ypy_yjs.py
@@ -53,13 +53,15 @@ def source(self):
 async def test_ypy_yjs_0(yws_server, yjs_client):
     ydoc = Y.YDoc()
     ynotebook = YNotebook(ydoc)
-    websocket = await connect("ws://localhost:1234/my-roomname")
-    WebsocketProvider(ydoc, websocket)
-    nb = stringify_source(json.loads((files_dir / "nb0.ipynb").read_text()))
-    ynotebook.source = nb
-    ytest = YTest(ydoc, 3.0)
-    await ytest.change()
-    assert ytest.source == nb
+
+    async with connect("ws://localhost:1234/my-roomname") as websocket, WebsocketProvider(
+        ydoc, websocket
+    ):
+        nb = stringify_source(json.loads((files_dir / "nb0.ipynb").read_text()))
+        ynotebook.source = nb
+        ytest = YTest(ydoc, 3.0)
+        await ytest.change()
+        assert ytest.source == nb
 
 
 def test_plotly_renderer():