diff --git a/rest-api-spec/api/indices.delete.json b/rest-api-spec/api/indices.delete.json
index d062ae8d5be2..711bd4e11e9d 100644
--- a/rest-api-spec/api/indices.delete.json
+++ b/rest-api-spec/api/indices.delete.json
@@ -8,6 +8,7 @@
       "parts": {
         "index": {
           "type" : "list",
+          "required" : true,
           "description" : "A comma-separated list of indices to delete; use `_all` or `*` string to delete all indices"
         }
       },