diff --git a/spec/schemas/rollups._common.yaml b/spec/schemas/rollups._common.yaml
index b67cc093..e97c0f7d 100644
--- a/spec/schemas/rollups._common.yaml
+++ b/spec/schemas/rollups._common.yaml
@@ -41,6 +41,8 @@ components:
           type: string
         target_index:
           type: string
+        target_index_settings:
+          $ref: '../schemas/indices._common.yaml#/components/schemas/IndexSettings'
         metadata_id:
           type: ['null', string]
         page_size: