diff --git a/runtime/indent/dtd.vim b/runtime/indent/dtd.vim
index 4350dfb..88c0c51 100644
--- a/runtime/indent/dtd.vim
+++ b/runtime/indent/dtd.vim
@@ -322,3 +322,4 @@
 endfunction
 
 let &cpo = s:cpo_save
+unlet s:cpo_save