diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f69045f03..c6bbce7e0 100755
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,9 @@
 2009-10-17  John Wiegley  <johnw@newartisans.com>
 
+	* org-clock.el (org-clock-in): Before creating
+	`org-clock-mode-line-timer', check to make sure an older timer is
+	not currently running.
+
 	* org.el (org-files-list): New utility function for returning a
 	list of all open org-mode buffers, plus all files used to build
 	the agenda buffer.  Note that not all the files will necessarily
diff --git a/lisp/org-clock.el b/lisp/org-clock.el
index 97e555221..587c7249a 100644
--- a/lisp/org-clock.el
+++ b/lisp/org-clock.el
@@ -616,6 +616,9 @@ the clocking selection, associated with the letter `d'."
 		(setq global-mode-string
 		      (append global-mode-string '(org-mode-line-string))))
 	    (org-clock-update-mode-line)
+	    (when org-clock-mode-line-timer
+	      (cancel-timer org-clock-mode-line-timer)
+	      (setq org-clock-mode-line-timer nil))
 	    (setq org-clock-mode-line-timer
 		  (run-with-timer 60 60 'org-clock-update-mode-line))
 	    (message "Clock starts at %s - %s" ts msg-extra)