Using custom RoleClaimType on OAuthBearer middleware

The OAuth server issues role claims using different claim type from System.Security.Claims.ClaimTypes.Role:

var adminRole = new Claim("CustomRole", "Admin");
context.Ticket.Identity.AddClaim(adminRole);

How can I tell the OAuthBearerAuthentication middleware to use my custom role claim type so it gets the Authorize attribute to work:

//Startup
app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions ...

[Authorize(Roles = "Admin")]
public IHttpActionResult SecureAction()

In OnValidateIdentity function of OAuthBearerAuthenticationProvider, we can rebind ClaimsIdentity with appropriate RolaClaimType and NameClaimType:

app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions
{
    Provider = new OAuthBearerAuthenticationProvider
    {
        OnValidateIdentity = context =>
        {
            var claimsIdentity = new ClaimsIdentity(
                context.Ticket.Identity.Claims,
                OAuthDefaults.AuthenticationType,
                CustomClaimTypes.Name,
                CustomClaimTypes.Role);

            context.Validated(claimsIdentity);

            return Task.FromResult(0);
        }
    }
});