diff --git a/runtime/ftplugin/plaintex.vim b/runtime/ftplugin/plaintex.vim
index 5862d00..9e0e402 100644
--- a/runtime/ftplugin/plaintex.vim
+++ b/runtime/ftplugin/plaintex.vim
@@ -32,5 +32,6 @@
 endif " exists("loaded_matchit")
 
 let &cpo = s:save_cpo
+unlet s:save_cpo
 
 " vim:sts=2:sw=2: