Doesn't filter out attribute options that are out of stock if one is already selected

When you first view the product form, all attribute options are available, even if the combinations of said attributes would be out of stock. Once you select an option from one of the attributes, then the filtering works as it should -- but only on one field at a time.

For example:

Two attributes: Size and Color, where there are three options available for each attribute (Size: Large, Medium, and Small) & (Color: Red, Green, and Blue). There is no stock of Large Red, Medium Green, or Small Blue items. The default selections for the product is Blue & Large. This makes sense, because that combination is in stock. If you select green from the color menu, the invalid option (medium) is filtered out as it should be. You are now selecting Green & Large. But if you then try to change the size, you'll see that Red is available as an option -- even though Red & Large is out of stock.

From what I can tell, no matter what combination of choices you pick, only the opposite attributes options are filtered -- the options in the box you are selecting from stay the same --allowing you to pick an invalid (and out of stock) combination on the next selection attempt.

I recently updated to beta12, and this issue popped up. It wasn't a problem before, but sadly I wasn't paying attention, and don't remember what version I was running before the update...