diff --git a/runtime/indent/cs.vim b/runtime/indent/cs.vim
index 064ab00..4a040b6 100644
--- a/runtime/indent/cs.vim
+++ b/runtime/indent/cs.vim
@@ -11,3 +11,5 @@
 
 " C# is like indenting C
 setlocal cindent
+
+let b:undo_indent = "setl cin<"