diff --git a/ably/realtime/connection.py b/ably/realtime/connection.py
index f698e18d..01f6ea75 100644
--- a/ably/realtime/connection.py
+++ b/ably/realtime/connection.py
@@ -195,7 +195,7 @@ async def send_protocol_message(self, protocolMessage):
 
     async def setup_ws(self):
         headers = HttpUtils.default_headers()
-        ws_url = f'wss://{self.options.realtime_host}?key={self.__ably.key}'
+        ws_url = f'wss://{self.options.get_realtime_host()}?key={self.__ably.key}'
         log.info(f'setup_ws(): attempting to connect to {ws_url}')
         async with websockets.connect(ws_url, extra_headers=headers) as websocket:
             log.info(f'setup_ws(): connection established to {ws_url}')