When adding same product several times from product page the price tiers are not honoured

1. Set up a product with price tiers 1 and 3
2. Go to that product page on sf
3. Press "Add to cart" button 3 times
4. Go to cart page and observe the price
Actual: the price used is the tier 1 price
P.S. when you click "Update" button on cart page the price changes to tier 3.
I think the current quantity in basket for item is ignored when we calculate the price