diff -u semantic-1.4/semantic-util-modes.el.orig semantic-1.4/semantic-util-modes.el
--- semantic-1.4/semantic-util-modes.el.orig	2002-06-24 23:01:40.000000000 +0900
+++ semantic-1.4/semantic-util-modes.el	2002-12-04 02:01:08.000000000 +0900
@@ -338,9 +338,11 @@
 
 (defface semantic-unmatched-syntax-face
   '((((class color) (background dark))
-     (:underline "red"))
+;     (:underline "red"))
+     (:background "red" :underline t))
     (((class color) (background light))
-     (:underline "red")))
+;     (:underline "red")))
+     (:background "red" :underline t)))
   "*Face used to show unmatched-syntax in.
 The face is used in  `semantic-show-unmatched-syntax-mode'."
   :group 'semantic)