UI text disappears in Editor after switching to another app and returning to Unity

In Unity 5.1.0f3 on OS X 10.9.5, if I switch away from Unity to another application then return to Unity, all text in UI elements will disappear (sometimes immediately, sometimes after half a second or so), in both Scene and Game windows. If I resize the Scene/Game window, the text will immediately redraw.

Anyone else have this problem? If it's not just me, happy to file a bug report.