QMenu action's checked status isn't shown if an icon is also present

If I create a QMenu with a QAction that is both checked (setCheckable(true)) and has an icon (setIcon(icon)), then render it using a custom stylesheet, the checked status isn't shown.

I've attached a project that demonstrates the problem (tested using Qt 5.6.3 and 5.9.2). If I disable the stylesheet, the checked indicator (either a checkmark or a border/background) correctly appears for the Cocoa, Fusion, and Windows styles. But when I enable a custom stylesheet, no checked indicator shows. Screenshots attached.