diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index 2ab109497..443f40f28 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -2400,6 +2400,7 @@ meta_window_x11_update_input_region (MetaWindow *window)
   g_autoptr (MtkRegion) region = NULL;
   MetaWindowX11 *window_x11 = META_WINDOW_X11 (window);
   MetaWindowX11Private *priv = meta_window_x11_get_instance_private (window_x11);
+  MtkRectangle bounding_rect = { 0 };
   Window xwindow;
 
   if (window->decorated)
@@ -2411,10 +2412,14 @@ meta_window_x11_update_input_region (MetaWindow *window)
           return;
         }
       xwindow = window->frame->xwindow;
+      bounding_rect.width = window->buffer_rect.width;
+      bounding_rect.height = window->buffer_rect.height;
     }
   else
     {
       xwindow = priv->xwindow;
+      bounding_rect.width = priv->client_rect.width;
+      bounding_rect.height = priv->client_rect.height;
     }
 
   if (META_X11_DISPLAY_HAS_SHAPE (x11_display))
@@ -2458,8 +2463,8 @@ meta_window_x11_update_input_region (MetaWindow *window)
       else if (n_rects == 1 &&
                (rects[0].x == 0 &&
                 rects[0].y == 0 &&
-                rects[0].width == window->buffer_rect.width &&
-                rects[0].height == window->buffer_rect.height))
+                rects[0].width == bounding_rect.width &&
+                rects[0].height == bounding_rect.height))
         {
           /* This is the bounding region case. Keep the
            * region as NULL. */
@@ -2476,13 +2481,6 @@ meta_window_x11_update_input_region (MetaWindow *window)
 
   if (region != NULL)
     {
-      MtkRectangle bounding_rect;
-
-      bounding_rect.x = 0;
-      bounding_rect.y = 0;
-      bounding_rect.width = window->buffer_rect.width;
-      bounding_rect.height = window->buffer_rect.height;
-
       /* The shape we get back from the client may have coordinates
        * outside of the frame. The X SHAPE Extension requires that
        * the overall shape the client provides never exceeds the