Size of opacity window for popup

When I use a popup window with opacity or a WebWaitMessage, the opaque background covers the parent form properly unless the parent window is scrollable. In this case the section outside the normal screen size is not opaque.

How can I control this so that when the user scrolls down the whole of the parent is covered by the child opaque window.

At this moment it covers entire visible window size but when scrolling is possible on the page, it is indeed not covering the non visible window part. We'll investigate to solve this.

Thanks Bruno.
Any idea of when this might be resolved?
I am just waiting on this to release my web app.