diff --git a/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go b/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
index 6b894ad15..63cfa266b 100644
--- a/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
+++ b/src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go
@@ -295,6 +295,7 @@ func (s *eventStatements) bulkSelectEventReference(eventNIDs []types.EventNID) (
 	return results, nil
 }
 
+// bulkSelectEventID returns a map from numeric event ID to string event ID.
 func (s *eventStatements) bulkSelectEventID(eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
 	rows, err := s.bulkSelectEventIDStmt.Query(eventNIDsAsArray(eventNIDs))
 	if err != nil {