diff --git a/gtk/gtklayoutmanager.c b/gtk/gtklayoutmanager.c
index 57746fd03e..6467b8ee5a 100644
--- a/gtk/gtklayoutmanager.c
+++ b/gtk/gtklayoutmanager.c
@@ -424,6 +424,7 @@ gtk_layout_manager_get_request_mode (GtkLayoutManager *manager)
   GtkLayoutManagerClass *klass;
 
   g_return_val_if_fail (GTK_IS_LAYOUT_MANAGER (manager), GTK_SIZE_REQUEST_CONSTANT_SIZE);
+  g_return_val_if_fail (priv->widget != NULL, GTK_SIZE_REQUEST_CONSTANT_SIZE);
 
   klass = GTK_LAYOUT_MANAGER_GET_CLASS (manager);