Google Maps API v3 - Markers hiding behind OverlayImage

In the past, Markers on this website appeared开发者_C百科 on top of the OverlayImage. But now they seem to render behind the Overlay:

Nashville Dining Map

How do I impact the z-order of Markers vs. the OverlayImage itself?

---

Markers seem to appear just fine, but you can set the markers z-index with setZIndex(zIndex:number) method.