How to configure overflow in twitter boot buffer drop-down list using submenu?

I have a problem with CSS overflow property for twitter dropdown bootstrap component with submenu.

When setting the maximum height and overflow for automatic display, the scroll bar appears in the list as it should, but the submenus appear in the drop-down list under the horizontal scroll bar, which is not what I need.

Here is an example of this problem.

http://jsfiddle.net/ftMhv/1/

I tried changing the values ​​of overflow-x and overflow-y, but none of them worked well.