UICollectionView: How to add space between Footer and Header?

I have a CollectionView using the standard FlowLayout class with horizontal scrolling and a header and footer in each section.

Now there's zero pixels between the footer and the header views (i.e between the sections). I'd like to add a little spacing between them, but not above the first section or after the last one. So I can't just add that space in the header and footer views itself.

I would have expected something like "interSectionSpacing", but apparently there is no such setting. Any ideas?