diff --git a/rest-api-spec/src/main/resources/rest-api-spec/api/delete_by_query.json b/rest-api-spec/src/main/resources/rest-api-spec/api/delete_by_query.json
index 0f2e14a336ff3..06da40bf04117 100644
--- a/rest-api-spec/src/main/resources/rest-api-spec/api/delete_by_query.json
+++ b/rest-api-spec/src/main/resources/rest-api-spec/api/delete_by_query.json
@@ -173,9 +173,9 @@
         "description":"The throttle for this request in sub-requests per second. -1 means no throttle."
       },
       "slices":{
-        "type":"number",
+        "type":"number|auto",
         "default":1,
-        "description":"The number of slices this task should be divided into. Defaults to 1 meaning the task isn't sliced into subtasks."
+        "description":"The number of slices this task should be divided into. Defaults to 1, meaning the task isn't sliced into subtasks."
       }
     },
     "body":{