diff --git a/docs/reference/indices/upgrade.asciidoc b/docs/reference/indices/upgrade.asciidoc
index 6840b69c404..af1ce4f5626 100644
--- a/docs/reference/indices/upgrade.asciidoc
+++ b/docs/reference/indices/upgrade.asciidoc
@@ -36,7 +36,7 @@ you want to upgrade at the same time.
 
 [source,sh]
 --------------------------------------------------
-curl 'http://localhost:9200/twitter/_upgrade?human'
+curl 'http://localhost:9200/twitter/_upgrade?pretty&human'
 --------------------------------------------------
 
 [source,js]