Can't close Mockups from the OSX dock icon?

The title says most of it - Right-clicking on the dock icon of Mockups Desktop in OSX, and selecting "Quit", doesn't close the app (at least for me). Pretty small thing (I have Mockups open almost all the time, so I don't hit this much =), but it's worth including as part of "make the app seem more native".

(I'm on a slightly older mockups build - 1.6.25. Forgive me if it's been fixed since, but I didn't see it mentioned here).