_ref is undefined

[jsonmaur]

If I don't pass any options to routerForBrowser(), I get the error _ref is undefined. Passing an empty object routerForBrowser({}) removes that error, but brings me to another error: "Missing route configuration...". I'm not totally clear on why this route configuration is necessary if I'm not passing route-specific data and just using Fragments? Things seem to work fine when it's an empty object (routerForBrowser({ routes: {} }).