How to always default route for every request

I am using ASP.NET 5 / MVC 6 and I am hosting a AngularJS SPA.

I am using UI Router, which works fine, but when I refresh the page on a route, for example /customer/5 I get a blank page. I expect this is because I haven't got a route / controller associated with that route.

Ideally in this case I would want MVC to serve up "index.html" (my default page) that contains all my AngularJS code and then let UI router show the correct page.

How do I do this? Here is a subset of my current Configure function in Startup.cs

app.UseMvc();
app.UseDefaultFiles();

app.UseStaticFiles();