Correct way of loading SSL certificate signed by Intermediate CA in Kestrel .NET Core

I am setting up SSL on my Kestrel Linux server using .NET Core 2.1.1.

The SSL certificate is signed by an intermediate CA.

The PFX contains the intermediate and root CA cert.

I load the pfx file as a X509Certificate2 object and use this for the server certificate.

It seems to be that the way I have set this up, the intermediate CA is not sent as part of the handshake and only the leaf is sent (this is very naughty).

return WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .UseKestrel(options =>
            {
                options.Listen(IPAddress.Any,443, listenOptions =>
                {

                    listenOptions.UseHttps("ssl.pfx", "password123");

                });
            }
            )
        .Build();

So I execute this command and it shows only the leaf but not the intermediate:

openssl s_client -showcerts -connect myserver:443

I expect it to include the intermediate ca and leaf as one would expect like this:

openssl s_client -showcerts -connect google.com:443