duplicate definition.
        (wl-summary-define-mark-action): Functions wl-summary-*-region
        keep current position.
+       (wl-summary-unregister-target-mark): Store result to the variable.
 
 2003-07-24  Yuuichi Teranishi  <teranisi@gohome.org>
 
 
            (cons number wl-summary-buffer-target-mark-list))))
 
 (defun wl-summary-unregister-target-mark (number)
-  (delq number wl-summary-buffer-target-mark-list))
+  (setq wl-summary-buffer-target-mark-list
+       (delq number wl-summary-buffer-target-mark-list)))
 
 (defun wl-summary-have-target-mark-p (number)
   (memq number wl-summary-buffer-target-mark-list))
     (let ((buffer-read-only nil)
          visible mark action)
       (if number
-         (setq visible (wl-summary-jump-to-msg number))
+         (setq visible (wl-summary-jump-to-msg number)) ; can be nil
        (setq visible t))
       (setq number (or number (wl-summary-message-number)))
       ;; Delete mark on buffer.