diff --git a/rootfs/scheduler/resources/pod.py b/rootfs/scheduler/resources/pod.py
index 92d93726a..99cd7b692 100644
--- a/rootfs/scheduler/resources/pod.py
+++ b/rootfs/scheduler/resources/pod.py
@@ -552,7 +552,7 @@ def events(self, pod):
         if not events:
             events = []
         # make sure that events are sorted
-        events.sort(key=lambda x: x['lastTimestamp'])
+        events.sort(key=lambda x: x['lastTimestamp'] or '')
         return events
 
     def _handle_pod_errors(self, pod, reason, message):