Prototype: slide in overlay doesn't scroll to reveal content below the fold

I have a prototype where I have a ‘nav menu’ slide in overlay from the right with links to page. When the browser window is small some of the links in the ‘nav menu’ are below the fold and I can’t scroll in the prototype to get to the bottom links.

Attcahed a screenshot of the overlay setup just in case:

Any help is much appreciated! 🙂

Thanks, Balazs