diff --git a/api/src/dooris_api/mqtt_client.py b/api/src/dooris_api/mqtt_client.py
index 2660951..3df1f19 100644
--- a/api/src/dooris_api/mqtt_client.py
+++ b/api/src/dooris_api/mqtt_client.py
@@ -155,7 +155,7 @@ class AsyncMqttClient:
         await self.fut_connected
 
         # re-establish all supposed mqtt subscriptions
-        if len(self.active_subscriptions > 0):
+        if len(self.active_subscriptions) > 0:
             qos = 1
             await self.client.subscribe((i, qos) for i in self.active_subscriptions)