diff --git a/lib/searchkick/relation_indexer.rb b/lib/searchkick/relation_indexer.rb
index 7ab58be..fc7b4bb 100644
--- a/lib/searchkick/relation_indexer.rb
+++ b/lib/searchkick/relation_indexer.rb
@@ -134,7 +134,7 @@ module Searchkick
     end
 
     def batch_job(class_name, batch_id, record_ids)
-      Searchkick.with_redis { |r| r.sadd(batches_key, batch_id) }
+      Searchkick.with_redis { |r| r.sadd(batches_key, [batch_id]) }
       Searchkick::BulkReindexJob.perform_later(
         class_name: class_name,
         index_name: index.name,
--
libgit2 0.21.0