diff --git a/app/models/alarms.py b/app/models/alarms.py
index a272e72..9e9685f 100644
--- a/app/models/alarms.py
+++ b/app/models/alarms.py
@@ -31,6 +31,9 @@ class Alarm(db.Model):  # type: ignore
     def update_state(self, state: AlarmState, text: str) -> None:
         from app.models.activity import Activity
 
+        if self.alarm_state is None:
+            self.alarm_state = AlarmState.UNKNOWN
+
         if self.alarm_state != state or self.state_changed is None:
             self.state_changed = datetime.utcnow()
             activity = Activity(activity_type="alarm_state",