1 files changed, 1 insertions, 2 deletions
diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index 774ecd81b6..3ad483efe0 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -536,8 +536,7 @@ class FederationSender(AbstractFederationSender):
 
                 if event_entries:
                     now = self.clock.time_msec()
-                    last_id = next(reversed(event_ids))
-                    ts = event_to_received_ts[last_id]
+                    ts = max(t for t in event_to_received_ts.values() if t)
                     assert ts is not None
 
                     synapse.metrics.event_processing_lag.labels(