diff --git a/runtime/ftplugin/hog.vim b/runtime/ftplugin/hog.vim
index 4ee0a9f934..61714f2db9 100644
--- a/runtime/ftplugin/hog.vim
+++ b/runtime/ftplugin/hog.vim
@@ -2,13 +2,14 @@
 " Language:     hog (snort.conf)
 " Maintainer: . Victor Roemer, <vroemer@badsec.org>.
 " Last Change:  Mar 1, 2013
+" 2025 Dec 03 by Vim Project: set undo_ftplugin correctly #18727
 
 if exists("b:did_ftplugin")
     finish
 endif
 let b:did_ftplugin = 1
 
-let s:undo_ftplugin = "setl fo< com< cms< def< inc<"
+let b:undo_ftplugin = "setl fo< com< cms< def< inc<"
 
 let s:cpo_save = &cpo
 set cpo&vim
@@ -19,8 +20,8 @@ setlocal commentstring=\c#\ %s
 setlocal define=\c^\s\{-}var
 setlocal include=\c^\s\{-}include
 
-" Move around configurations 
-let s:hog_keyword_match = '\c^\s*\<\(preprocessor\\|config\\|output\\|include\\|ipvar\\|portvar\\|var\\|dynamicpreprocessor\\|' . 
+" Move around configurations
+let s:hog_keyword_match = '\c^\s*\<\(preprocessor\\|config\\|output\\|include\\|ipvar\\|portvar\\|var\\|dynamicpreprocessor\\|' .
                         \ 'dynamicengine\\|dynamicdetection\\|activate\\|alert\\|drop\\|block\\|dynamic\\|log\\|pass\\|reject\\|sdrop\\|sblock\)\>'
 
 exec "nnoremap <buffer><silent> ]] :call search('" . s:hog_keyword_match . "', 'W' )<CR>"
@@ -28,9 +29,9 @@ exec "nnoremap <buffer><silent> [[ :call search('" . s:hog_keyword_match . "', '
 
 if exists("loaded_matchit")
     let b:match_words =
-                  \ '^\s*\<\%(preprocessor\|config\|output\|include\|ipvar\|portvar' . 
-                  \ '\|var\|dynamicpreprocessor\|dynamicengine\|dynamicdetection' . 
-                  \ '\|activate\|alert\|drop\|block\|dynamic\|log\|pass\|reject' . 
+                  \ '^\s*\<\%(preprocessor\|config\|output\|include\|ipvar\|portvar' .
+                  \ '\|var\|dynamicpreprocessor\|dynamicengine\|dynamicdetection' .
+                  \ '\|activate\|alert\|drop\|block\|dynamic\|log\|pass\|reject' .
                   \ '\|sdrop\|sblock\>\):$,\::\,:;'
     let b:match_skip = 'r:\\.\{-}$\|^\s*#.\{-}$\|^\s*$'
 endif