diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index fd40b44a9..dc47425c2 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -201,7 +201,7 @@ class SearchStore(BackgroundUpdateStore):
                 "target_min_stream_id_inclusive": target_min_stream_id,
                 "max_stream_id_exclusive": min_stream_id,
                 "rows_inserted": rows_inserted + len(rows),
-                "have_added_index": True,
+                "have_added_indexes": True,
             }
 
             self._background_update_progress_txn(