I've had a customer telling me today that they couldn't get past the shopping cart page, after much investigation it has become apparent that it is because the item they previously had saved in their cart is now out of stock.

For some reason the shopping cart in this situation is not flagging a message saying that the item is out of stock.

Is this normal? If so any way of adding something to provide a message stack to alert the customer a product in their cart is no longer available?