--- tasklist-widget-ORIG.c	2014-02-16 03:38:19.000000000 +0100
+++ tasklist-widget.c	2014-04-25 01:52:27.303520561 +0200
@@ -3819,7 +3819,10 @@
 
           /* update the icon (we use another size for
            * icon box mode) */
-          xfce_tasklist_button_icon_changed (child->window, child);
+          if (child->type == CHILD_TYPE_GROUP)
+            xfce_tasklist_group_button_icon_changed (child->class_group, child);
+          else
+            xfce_tasklist_button_icon_changed (child->window, child);
         }
     }
 }