diff --git a/src/compositor/meta-window-actor-x11.c b/src/compositor/meta-window-actor-x11.c
index 815cf84dd..04575ba70 100644
--- a/src/compositor/meta-window-actor-x11.c
+++ b/src/compositor/meta-window-actor-x11.c
@@ -384,6 +384,9 @@ has_shadow (MetaWindowActorX11 *actor_x11)
 {
   MetaWindow *window =
     meta_window_actor_get_meta_window (META_WINDOW_ACTOR (actor_x11));
+  MetaWindowX11 *x11_window = META_WINDOW_X11 (window);
+  MetaWindowX11Private *priv =
+    meta_window_x11_get_private (x11_window);
 
   if (actor_x11->shadow_mode == META_SHADOW_MODE_FORCED_OFF)
     return FALSE;
@@ -422,7 +425,7 @@ has_shadow (MetaWindowActorX11 *actor_x11)
    * If a window specifies that it has custom frame extents, that likely
    * means that it is drawing a shadow itself. Don't draw our own.
    */
-  if (window->has_custom_frame_extents)
+  if (priv->has_custom_frame_extents)
     return FALSE;
 
   /*
diff --git a/src/core/window-private.h b/src/core/window-private.h
index 9fc74f145..22f88e768 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -302,7 +302,6 @@ struct _MetaWindow
      know about for this window */
   guint32 net_wm_user_time;
 
-  gboolean has_custom_frame_extents;
   MetaFrameBorder custom_frame_extents;
 
   /* The rectangles here are in "frame rect" coordinates. See the
diff --git a/src/core/window.c b/src/core/window.c
index 63305207e..12215abec 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -6010,35 +6010,6 @@ meta_window_get_tile_area (MetaWindow   *window,
     tile_area->x += work_area.width - tile_area->width;
 }
 
-/**
- * meta_window_is_client_decorated:
- *
- * Check if if the window has decorations drawn by the client.
- *
- * `window->decorated` refers only to whether we should add decorations.
- */
-gboolean
-meta_window_is_client_decorated (MetaWindow *window)
-{
-  if (window->client_type == META_WINDOW_CLIENT_TYPE_WAYLAND)
-    {
-      /* Assume all Wayland clients draw decorations - not strictly
-       * true but good enough for current purposes.
-       */
-      return TRUE;
-    }
-  else
-    {
-      /* Currently the implementation here is hackish -
-       * has_custom_frame_extents() is set if _GTK_FRAME_EXTENTS is set
-       * to any value even 0. GTK+ always sets _GTK_FRAME_EXTENTS for
-       * client-side-decorated window, even if the value is 0 because
-       * the window is maxized and has no invisible borders or shadows.
-       */
-      return window->has_custom_frame_extents;
-    }
-}
-
 /**
  * meta_window_foreach_transient:
  * @window: a #MetaWindow
diff --git a/src/meta/window.h b/src/meta/window.h
index d6f7e0e31..41bedd2ca 100644
--- a/src/meta/window.h
+++ b/src/meta/window.h
@@ -423,9 +423,6 @@ gboolean meta_window_allows_move (MetaWindow *window);
 META_EXPORT
 gboolean meta_window_allows_resize (MetaWindow *window);
 
-META_EXPORT
-gboolean meta_window_is_client_decorated (MetaWindow *window);
-
 META_EXPORT
 gboolean meta_window_titlebar_is_onscreen    (MetaWindow *window);
 
diff --git a/src/x11/window-props.c b/src/x11/window-props.c
index cbed79f34..3f6796dfd 100644
--- a/src/x11/window-props.c
+++ b/src/x11/window-props.c
@@ -324,13 +324,16 @@ meta_window_set_custom_frame_extents (MetaWindow      *window,
                                       MetaFrameBorder *extents,
                                       gboolean         is_initial)
 {
+  MetaWindowX11 *window_x11 = META_WINDOW_X11 (window);
+  MetaWindowX11Private *priv =
+    meta_window_x11_get_private (window_x11);
   if (extents)
     {
-      if (window->has_custom_frame_extents &&
+      if (priv->has_custom_frame_extents &&
           memcmp (&window->custom_frame_extents, extents, sizeof (MetaFrameBorder)) == 0)
         return;
 
-      window->has_custom_frame_extents = TRUE;
+      priv->has_custom_frame_extents = TRUE;
       window->custom_frame_extents = *extents;
 
       /* If we're setting the frame extents on map, then this is telling
@@ -346,10 +349,10 @@ meta_window_set_custom_frame_extents (MetaWindow      *window,
     }
   else
     {
-      if (!window->has_custom_frame_extents)
+      if (!priv->has_custom_frame_extents)
         return;
 
-      window->has_custom_frame_extents = FALSE;
+      priv->has_custom_frame_extents = FALSE;
       memset (&window->custom_frame_extents, 0, sizeof (window->custom_frame_extents));
     }
 
diff --git a/src/x11/window-x11-private.h b/src/x11/window-x11-private.h
index c947744ee..96bc05618 100644
--- a/src/x11/window-x11-private.h
+++ b/src/x11/window-x11-private.h
@@ -100,6 +100,7 @@ struct _MetaWindowX11Private
   /* maintained by group.c */
   MetaGroup *group;
 
+  gboolean has_custom_frame_extents;
   MetaSyncCounter sync_counter;
 
   /* Used by keybindings.c */
diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index 0c7a7f9dc..f826cbb66 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -2607,6 +2607,8 @@ meta_window_move_resize_request (MetaWindow  *window,
                                  int          new_width,
                                  int          new_height)
 {
+  MetaWindowX11Private *priv =
+    meta_window_x11_get_private (META_WINDOW_X11 (window));
   int x, y, width, height;
   gboolean allow_position_change;
   gboolean in_grab_op;
@@ -2763,7 +2765,7 @@ meta_window_move_resize_request (MetaWindow  *window,
            * the monitor.
            */
           if (meta_prefs_get_force_fullscreen() &&
-              (window->decorated || !meta_window_is_client_decorated (window)) &&
+              (window->decorated || !priv->has_custom_frame_extents) &&
               mtk_rectangle_equal (&rect, &monitor_rect) &&
               window->has_fullscreen_func &&
               !window->fullscreen)