@@ -2500,12 +2520,24 @@ mouse-drag-and-drop-region
             ;; text will be inserted to inside of the original
             ;; region.
             (setq drag-but-negligible
-                  (and (eq (overlay-buffer mouse-drag-and-drop-overlay)
+                  (and (eq (overlay-buffer (car mouse-drag-and-drop-overlays))
                            buffer-to-paste)
-                       (<= (overlay-start mouse-drag-and-drop-overlay)
-                          point-to-paste)
-                       (<= point-to-paste
-                          (overlay-end mouse-drag-and-drop-overlay)))))
+                       (if region-noncontiguous
+                           ;; If the region is rectangular, check if the newly inserted
+                           ;; rectangular text would intersect the already selected
+                           ;; region. If it would, then set "drag-but-negligible" to t.
+                           (let ((size (cons region-width region-height)))
+                             (and (rectangle-intersect-p
+                                   (rectangle-position-as-coordinates start) size
+                                   (rectangle-position-as-coordinates point-to-paste) size)
+                                  (or (not (= (line-number-at-pos start)
+                                              (line-number-at-pos point-to-paste)))
+                                      (and (<= start point-to-paste)
+                                           (<= point-to-paste (+ start (car size)))))))
+                         (and (<= (overlay-start (car mouse-drag-and-drop-overlays))
+                                  point-to-paste)
+                              (<= point-to-paste
+                                  (overlay-end (car mouse-drag-and-drop-overlays))))))))
 
           ;; Show a tooltip.
           (if mouse-drag-and-drop-region-show-tooltip