diff --git a/broadcaster/backends/base.py b/broadcaster/backends/base.py
index 0a7ab24..d5b1d14 100644
--- a/broadcaster/backends/base.py
+++ b/broadcaster/backends/base.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import asyncio
 from typing import Any
 
 from .._event import Event
@@ -29,6 +30,8 @@ async def next_published(self) -> Event:
 
 
 class BroadcastCacheBackend(BroadcastBackend):
+    _ready: asyncio.Event
+
     async def get_current_channel_id(self, channel: str):
         raise NotImplementedError()