diff --git a/runtime/ftplugin/help.vim b/runtime/ftplugin/help.vim
index 7e82081..46c844c 100644
--- a/runtime/ftplugin/help.vim
+++ b/runtime/ftplugin/help.vim
@@ -8,6 +8,6 @@
 endif
 let b:did_ftplugin = 1
 
-let b:undo_plugin = "setl fo< tw<"
+let b:undo_ftplugin = "setl fo< tw<"
 
 setlocal formatoptions+=tcroql textwidth=78