--- lisp/mouse.el
+++ lisp/mouse.el
@@ -927,6 +927,7 @@
 should only be used by mouse-drag-region."
   (mouse-minibuffer-check start-event)
   (setq mouse-selection-click-count-buffer (current-buffer))
+  (deactivate-mark)
   (let* ((original-window (selected-window))
          ;; We've recorded what we needed from the current buffer and
          ;; window, now let's jump to the place of the event, where things
@@ -971,7 +972,6 @@
     (mouse-move-drag-overlay mouse-drag-overlay start-point start-point
                              click-count)
     (overlay-put mouse-drag-overlay 'window start-window)
-    (deactivate-mark)
     (let (event end end-point last-end-point)
       (track-mouse
 	(while (progn