diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index 5a6f113b0..e32f07ffb 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -2092,32 +2092,34 @@ meta_window_move_resize_request (MetaWindow *window,
       rect.width = width;
       rect.height = height;
 
-      meta_screen_get_monitor_geometry (window->screen, window->monitor->number, &monitor_rect);
-
-      /* Workaround braindead legacy apps that don't know how to
-       * fullscreen themselves properly - don't get fooled by
-       * windows which hide their titlebar when maximized or which are
-       * client decorated; that's not the same as fullscreen, even
-       * if there are no struts making the workarea smaller than
-       * the monitor.
-       */
-      if (meta_prefs_get_force_fullscreen() &&
-          !window->hide_titlebar_when_maximized &&
-          (window->decorated || !meta_window_is_client_decorated (window)) &&
-          meta_rectangle_equal (&rect, &monitor_rect) &&
-          window->has_fullscreen_func &&
-          !window->fullscreen)
-        {
-          /*
-          meta_topic (META_DEBUG_GEOMETRY,
-          */
-          meta_warning (
-                      "Treating resize request of legacy application %s as a "
-                      "fullscreen request\n",
-                      window->desc);
-          meta_window_make_fullscreen_internal (window);
-        }
-
+      if (window->monitor) {
+
+        meta_screen_get_monitor_geometry (window->screen, window->monitor->number, &monitor_rect);
+
+        /* Workaround braindead legacy apps that don't know how to
+         * fullscreen themselves properly - don't get fooled by
+         * windows which hide their titlebar when maximized or which are
+         * client decorated; that's not the same as fullscreen, even
+         * if there are no struts making the workarea smaller than
+         * the monitor.
+         */
+        if (meta_prefs_get_force_fullscreen() &&
+            !window->hide_titlebar_when_maximized &&
+            (window->decorated || !meta_window_is_client_decorated (window)) &&
+            meta_rectangle_equal (&rect, &monitor_rect) &&
+            window->has_fullscreen_func &&
+            !window->fullscreen)
+          {
+            /*
+              meta_topic (META_DEBUG_GEOMETRY,
+            */
+            meta_warning (
+                          "Treating resize request of legacy application %s as a "
+                          "fullscreen request\n",
+                          window->desc);
+            meta_window_make_fullscreen_internal (window);
+          }
+      }
       adjust_for_gravity (window, TRUE, gravity, &rect);
       meta_window_client_rect_to_frame_rect (window, &rect, &rect);
       meta_window_move_resize_internal (window, flags, gravity, rect);