Guide me – changing opacity in a long listbox creates last elements disappear

Hello ..

Have formed a listbox with an Opacity set to a value less than 1 and when I connect a long list the last elements are disappearing.

I made a little sample to replicate the problem.

In the XAML a listbox -

bound to a long list -

public MainPage()
{
InitializeComponent();
List l = new List();
for (int i = 0; i < 100; i++)
{
l.Add(i);
}

this.DataContext = l;
}

having executed, the last element I look is "87", there is the rest for the others elements at the bottom however it is completely black.

The actual issue -

Some one referred to it as a problem with virtualization as the issue happens at the 87, and we have 29 items appearing on the screen (the listbox virtualizes 3 times the number of items shown, see - 3*29 = 87). I verified with an ItemsControl (without virtualization), and the problem is still there as it is.

Can someone pick the missing link here ??