diff --git a/gtk/gtkgrid.c b/gtk/gtkgrid.c
index f8a281e711..cbc3c34790 100644
--- a/gtk/gtkgrid.c
+++ b/gtk/gtkgrid.c
@@ -1603,10 +1603,14 @@ gtk_grid_get_child_at (GtkGrid *grid,
                        gint     left,
                        gint     top)
 {
-  GtkGridPrivate *priv = grid->priv;
+  GtkGridPrivate *priv;
   GtkGridChild *child;
   GList *list;
 
+  g_return_val_if_fail (GTK_IS_GRID (grid), NULL);
+
+  priv = grid->priv;
+
   for (list = priv->children; list; list = list->next)
     {
       child = list->data;