psppire_axis_impl_insert (PsppireAxisImpl *a, gint posn, gint size)
{
struct axis_node *before = NULL;
- struct axis_node *new_node = pool_alloc (a->pool, sizeof (*new_node));
+ struct axis_node *new_node;
+
+ g_return_if_fail ( posn < tower_height (&a->unit_tower));
+ g_return_if_fail ( posn >= 0);
+
+ new_node = pool_alloc (a->pool, sizeof (*new_node));
if ( posn > 0)
{