diff --git a/server/webserver.py b/server/webserver.py
index 325d730..cdf15d6 100644
--- a/server/webserver.py
+++ b/server/webserver.py
@@ -196,7 +196,9 @@ class WebServer:
         alert_ids = list(self.alerts.iterkeys())
         alerts = []
         for k in alert_ids:
-            alerts.append(self.alerts.get(k))
+            a = self.alerts.get(k)
+            if a is not None:
+                alerts.append(a)
         # We never want alerts that seem to be in the past
         alerts = list(filter(lambda alert: not alert.expired(), alerts))
         alerts = sorted(alerts, key=lambda alert: (alert.start_time if alert and alert.start_time else 0))