Index: hi-lock.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/hi-lock.el,v
retrieving revision 1.51
diff -u -r1.51 hi-lock.el
--- hi-lock.el	6 May 2008 07:57:38 -0000	1.51
+++ hi-lock.el	15 Jun 2008 09:42:35 -0000
@@ -421,7 +421,12 @@
    (list
     (hi-lock-regexp-okay
      (read-from-minibuffer "Regexp to highlight: "
-                           (cons (or (car hi-lock-regexp-history) "") 1 )
+                           (cons (or (when (eq last-command
+                                               'isearch-other-control-char)
+                                       (if isearch-regexp
+                                           isearch-string
+                                         (regexp-quote isearch-string)))
+                                     (car hi-lock-regexp-history) "") 1 )
                            nil nil 'hi-lock-regexp-history))
     (hi-lock-read-face-name)))
   (or (facep face) (setq face 'hi-yellow))