diff --git a/alarmdecoder/zonetracking.py b/alarmdecoder/zonetracking.py
index ae92eb7..6db4009 100644
--- a/alarmdecoder/zonetracking.py
+++ b/alarmdecoder/zonetracking.py
@@ -154,6 +154,7 @@ def update(self, message):
                 #       regular messages.
                 try:
                     self._update_zone(zone, status=status)
+                    self.zones[zone].expander = True
 
                 except IndexError:
                     self._add_zone(zone, status=status, expander=True)