diff -Nur original/plugins/tasklist/tasklist-widget.c modified/plugins/tasklist/tasklist-widget.c
--- original/plugins/tasklist/tasklist-widget.c	2015-02-28 16:37:36.000000000 +0000
+++ modified/plugins/tasklist/tasklist-widget.c	2015-09-05 16:16:03.799548200 +0100
@@ -2633,6 +2633,11 @@
       else
         gtk_widget_hide (child->button);
     }
+  /* initiate viewport switch on geometry change - fixes buttons not 
+   * getting updated when using compiz */
+  active_ws = wnck_screen_get_active_workspace (child->tasklist->screen);
+  if (wnck_workspace_is_virtual (active_ws))
+    xfce_tasklist_viewports_changed (child->tasklist->screen, child->tasklist);
 }