diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index a8c53e8e6..bb84cdafc 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -2094,30 +2094,33 @@ 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)
+      if (window->monitor)
         {
-          /*
-          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);
+          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);