diff --git a/wideq.py b/wideq.py
index c49a8af..6be5c20 100644
--- a/wideq.py
+++ b/wideq.py
@@ -953,8 +953,9 @@ class ACDevice(Device):
     def monitor_start(self):
         """Start monitoring the device's status."""
 
-        self.mon = Monitor(self.client.session, self.device.id)
-        self.mon.start()
+        mon = Monitor(self.client.session, self.device.id)
+        mon.start()
+        self.mon = mon
 
     def monitor_stop(self):
         """Stop monitoring the device's status."""
@@ -969,6 +970,10 @@ class ACDevice(Device):
         available.
         """
 
+        # Abort if monitoring has not started yet.
+        if not hasattr(self, 'mon'):
+            return None
+
         res = self.mon.poll_json()
         if res:
             return ACStatus(self, res)