diff --git a/libs/monitor/xaal/monitor/monitor.py b/libs/monitor/xaal/monitor/monitor.py
index 0b42ce9b6c21a536b5baa5df7e17bb8442e00813..1fff718fd5528d93289b5df96eeabb0dab4723a8 100644
--- a/libs/monitor/xaal/monitor/monitor.py
+++ b/libs/monitor/xaal/monitor/monitor.py
@@ -177,12 +177,12 @@ class Devices:
 
     def get_dev_types(self):
         """ return the list of distinct dev_types"""
-        l = []
+        ll = []
         for dev in self.__devs.values():
-            if dev.dev_type not in l:
-                l.append(dev.dev_type)
-        l.sort()
-        return l
+            if dev.dev_type not in ll:
+                ll.append(dev.dev_type)
+        ll.sort()
+        return ll
 
     def __len__(self):
         return len(self.__devs)
@@ -255,6 +255,8 @@ class Monitor:
             self.notify(Notification.new_device,dev)
 
         dev = self.devices.get_with_addr(msg.source)
+        if not dev:
+            return
 
         if msg.is_alive():
             dev.alive(msg.body.get('timeout', config.DEF_ALIVE_TIMER))