1 files changed, 3 insertions, 1 deletions
diff --git a/synapse/storage/databases/main/state_deltas.py b/synapse/storage/databases/main/state_deltas.py
index 7f3624b128..188afec332 100644
--- a/synapse/storage/databases/main/state_deltas.py
+++ b/synapse/storage/databases/main/state_deltas.py
@@ -56,7 +56,9 @@ class StateDeltasStore(SQLBaseStore):
         prev_stream_id = int(prev_stream_id)
 
         # check we're not going backwards
-        assert prev_stream_id <= max_stream_id
+        assert (
+            prev_stream_id <= max_stream_id
+        ), f"New stream id {max_stream_id} is smaller than prev stream id {prev_stream_id}"
 
         if not self._curr_state_delta_stream_cache.has_any_entity_changed(
             prev_stream_id