diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index 52f3642ddc..7a99d3098b 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -2478,7 +2478,8 @@ gdk_x11_window_set_geometry_hints (GdkWindow         *window,
   toplevel = _gdk_x11_window_get_toplevel (window);
   if (toplevel)
     {
-      toplevel->last_geometry_hints = *geometry;
+      if (geometry)
+        toplevel->last_geometry_hints = *geometry;
       toplevel->last_geometry_hints_mask = geom_mask;
     }