Update runtime files
diff --git a/runtime/indent/elm.vim b/runtime/indent/elm.vim
index 232c347..7b08de7 100644
--- a/runtime/indent/elm.vim
+++ b/runtime/indent/elm.vim
@@ -4,7 +4,7 @@
 " Original Author: Joseph Hager <ajhager@gmail.com>
 " Copyright: Joseph Hager <ajhager@gmail.com>
 " License: BSD3
-" Latest Revision: 2020-05-29
+" Latest Revision: 2021-09-29
 
 " Only load this indent file when no other was loaded.
 if exists('b:did_indent')
@@ -19,6 +19,8 @@
 setlocal nolisp
 setlocal nosmartindent
 
+let b:undo_indent = "setl et< inde< indk< lisp< si<"
+
 " Only define the function once.
 if exists('*GetElmIndent')
 	finish