--- a/runtime/ftplugin/ishd.vim
+++ b/runtime/ftplugin/ishd.vim
@@ -1,32 +1,37 @@
 " Vim filetype plugin file
-" Language:	InstallShield (ft=ishd)
-" Maintainer:	Johannes Zellner <johannes@zellner.org>
-" Last Change:	Sat, 24 May 2003 11:55:36 CEST
+" Language:		InstallShield (ft=ishd)
+" Maintainer:		Doug Kearns <dougkearns@gmail.com>
+" Previous Maintainer:	Johannes Zellner <johannes@zellner.org>
+" Last Change:		2023 Aug 28
 
 if exists("b:did_ftplugin") | finish | endif
 let b:did_ftplugin = 1
 
-setlocal foldmethod=syntax
-
 " Using line continuation here.
 let s:cpo_save = &cpo
 set cpo-=C
 
+setlocal foldmethod=syntax
+
+let b:undo_ftplugin = "setl fdm<"
+
 " matchit support
 if exists("loaded_matchit")
-    let b:match_ignorecase=0
-    let b:match_words=
+    let b:match_ignorecase = 0
+    let b:match_words =
     \ '\%(^\s*\)\@<=\<function\>\s\+[^()]\+\s*(:\%(^\s*\)\@<=\<begin\>\s*$:\%(^\s*\)\@<=\<return\>:\%(^\s*\)\@<=\<end\>\s*;\s*$,' .
     \ '\%(^\s*\)\@<=\<repeat\>\s*$:\%(^\s*\)\@<=\<until\>\s\+.\{-}\s*;\s*$,' .
     \ '\%(^\s*\)\@<=\<switch\>\s*(.\{-}):\%(^\s*\)\@<=\<\%(case\|default\)\>:\%(^\s*\)\@<=\<endswitch\>\s*;\s*$,' .
     \ '\%(^\s*\)\@<=\<while\>\s*(.\{-}):\%(^\s*\)\@<=\<endwhile\>\s*;\s*$,' .
     \ '\%(^\s*\)\@<=\<for\>.\{-}\<\%(to\|downto\)\>:\%(^\s*\)\@<=\<endfor\>\s*;\s*$,' .
     \ '\%(^\s*\)\@<=\<if\>\s*(.\{-})\s*then:\%(^\s*\)\@<=\<else\s*if\>\s*([^)]*)\s*then:\%(^\s*\)\@<=\<else\>:\%(^\s*\)\@<=\<endif\>\s*;\s*$'
+    let b:undo_ftplugin .= " | unlet! b:match_ignorecase b:match_words"
 endif
 
-if has("gui_win32") && !exists("b:browsefilter")
+if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
     let b:browsefilter = "InstallShield Files (*.rul)\t*.rul\n" .
-		       \ "All Files (*.*)\t*.*\n"
+          \              "All Files (*.*)\t*\n"
+    let b:undo_ftplugin .= " | unlet! b:browsefilter"
 endif
 
 let &cpo = s:cpo_save