=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2012-10-03 08:50:49 +0000
+++ lisp/ChangeLog	2012-10-03 14:26:48 +0000
@@ -1,3 +1,9 @@
+2012-10-03  Jambunathan K  <kjambunathan@gmail.com>
+
+	* register.el (append-to-register, prepend-to-register):
+	Deactivate mark.  This accords with current behaviour of
+	`copy-to-register'.  See (Bug#12389).
+
 2012-10-03  Martin Rudalics  <rudalics@gmx.at>
 
 	* menu-bar.el (kill-this-buffer): Don't do anything when

=== modified file 'lisp/register.el'
--- lisp/register.el	2012-09-09 08:10:56 +0000
+++ lisp/register.el	2012-10-03 13:21:46 +0000
@@ -382,6 +382,7 @@
      register (cond ((not reg) text)
                     ((stringp reg) (concat reg separator text))
                     (t (error "Register does not contain text")))))
+  (setq deactivate-mark t)
   (cond (delete-flag
 	 (delete-region start end))
 	((called-interactively-p 'interactive)
@@ -400,6 +401,7 @@
      register (cond ((not reg) text)
                     ((stringp reg) (concat text separator reg))
                     (t (error "Register does not contain text")))))
+  (setq deactivate-mark t)
   (cond (delete-flag
 	 (delete-region start end))
 	((called-interactively-p 'interactive)