diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index 87067955b..aeaebb7c7 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -4066,3 +4066,22 @@ meta_window_x11_always_update_shape (MetaWindow *window)
 
   return META_WINDOW_X11_GET_CLASS (window_x11)->always_update_shape (window);
 }
+
+void
+meta_window_x11_buffer_rect_to_frame_rect (MetaWindow    *window,
+                                           MetaRectangle *buffer_rect,
+                                           MetaRectangle *frame_rect)
+
+{
+  MetaFrameBorders borders;
+
+  g_return_if_fail (window->frame);
+
+  meta_frame_calc_borders (window->frame, &borders);
+
+  *frame_rect = *buffer_rect;
+  frame_rect->x += borders.invisible.left;
+  frame_rect->y += borders.invisible.top;
+  frame_rect->width -= borders.invisible.left + borders.invisible.right;
+  frame_rect->height -= borders.invisible.top + borders.invisible.bottom;
+}
diff --git a/src/x11/window-x11.h b/src/x11/window-x11.h
index 256bca568..03c52c5ab 100644
--- a/src/x11/window-x11.h
+++ b/src/x11/window-x11.h
@@ -89,4 +89,8 @@ void     meta_window_x11_set_thaw_after_paint    (MetaWindow *window,
 gboolean meta_window_x11_should_thaw_after_paint (MetaWindow *window);
 gboolean meta_window_x11_always_update_shape     (MetaWindow *window);
 
+void meta_window_x11_buffer_rect_to_frame_rect   (MetaWindow    *window,
+                                                  MetaRectangle *buffer_rect,
+                                                  MetaRectangle *frame_rect);
+
 #endif