Token validation stops working when using identity - asp.net

Question

I've added token (jwt) validation to my Web-API by following the steps in this tutorial. However, when I now try to add Asp.Net Identity to my application it somehow skips the token validation.
The token generation still works fine.
The API-controller-action that I am trying to access looks like this:
// GET api/users/5
[HttpGet("{id}")]
[Authorize]
public User Get(int id)
{
return _userService.FindById(id);
}
The "Authorize" attribute doesn't seem to make any difference after adding identity to my OWIN startup file, which looks like this:
var secretKey = "secret";
var signingKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(secretKey));
var audience = "aud";
var issuer = "iss";
var tokenValidationParameters = new TokenValidationParameters
{
ValidateIssuerSigningKey = true,
IssuerSigningKey = signingKey,
ValidateIssuer = true,
ValidIssuer = issuer,
ValidateAudience = true,
ValidAudience = audience,
ValidateLifetime = true,
ClockSkew = TimeSpan.Zero
};
app.UseJwtBearerAuthentication(new JwtBearerOptions
{
AutomaticAuthenticate = true,
AutomaticChallenge = true,
TokenValidationParameters = tokenValidationParameters
});
app.UseStaticFiles();
app.UseIdentity(); // When adding this the token-validation above seems to stop working...
var options = new TokenProviderOptions
{
Audience = audience,
Issuer = issuer,
SigningCredentials = new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256)
};
app.UseMiddleware<TokenProviderMiddleware>(Options.Create(options));
app.UseMvc();
I've tried moving the Identity middleware above JwtBearerAuth, with no luck.
It always seems to skip validating my token, and even if I leave out the token I am able to reach the action, but when I remove the Identity middleware the token-validation starts working again.