1 files changed, 6 insertions, 2 deletions
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index 60cdc884e6..a2f8c23a65 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -52,7 +52,9 @@ class BackgroundUpdatePerformance(object):
         Returns:
             A duration in ms as a float
         """
-        if self.total_item_count == 0:
+        if self.avg_duration_ms == 0:
+            return 0
+        elif self.total_item_count == 0:
             return None
         else:
             # Use the exponential moving average so that we can adapt to
@@ -64,7 +66,9 @@ class BackgroundUpdatePerformance(object):
         Returns:
             A duration in ms as a float
         """
-        if self.total_item_count == 0:
+        if self.total_duration_ms == 0:
+            return 0
+        elif self.total_item_count == 0:
             return None
         else:
             return float(self.total_item_count) / float(self.total_duration_ms)