diff --git a/ftplugin/markdown.vim b/ftplugin/markdown.vim
index e7fa241..009b45d 100644
--- a/ftplugin/markdown.vim
+++ b/ftplugin/markdown.vim
@@ -12,6 +12,10 @@ setlocal comments=fb:*,fb:-,fb:+,n:> commentstring=>\ %s
 setlocal formatoptions+=tcqln
 setlocal formatlistpat=^\\s*\\d\\+\\.\\s\\+\\\|^[-*+]\\s\\+
 
-let b:undo_ftplugin .= "|setl cms< com< fo<"
+if exists('b:undo_ftplugin')
+  let b:undo_ftplugin .= "|setl cms< com< fo< flp<"
+else
+  let b:undo_ftplugin = "setl cms< com< fo< flp<"
+endif
 
 " vim:set sw=2: