diff --git a/matrix_appservice_kakaotalk/rpc/rpc.py b/matrix_appservice_kakaotalk/rpc/rpc.py
index 59d8d84..ef48b99 100644
--- a/matrix_appservice_kakaotalk/rpc/rpc.py
+++ b/matrix_appservice_kakaotalk/rpc/rpc.py
@@ -83,11 +83,11 @@ class RPCClient:
         await self.request("register", peer_id=self.config["appservice.address"])
 
     async def disconnect(self) -> None:
-        assert self._writer is not None
-        self._writer.write_eof()
-        await self._writer.drain()
-        self._writer = None
-        self._reader = None
+        if self._writer is not None:
+            self._writer.write_eof()
+            await self._writer.drain()
+            self._writer = None
+            self._reader = None
 
     @property
     def _next_req_id(self) -> int: