Xamarin.Forms HttpClient.GetAsync Blocks UI Thread

Using await client.GetAsync(uri) blocks my UI thread.

Here's the code inside my button click event handler:

private async void Button_Clicked(object sender, EventArgs e)
    {
        var vm = new MainPageViewModel();

        HttpClient client = new HttpClient();
        client.MaxResponseContentBufferSize = 256000;

        var uri = new Uri(string.Format("http://localhost:50715/api/values"));

        var response = await client.GetAsync(uri); // This is where UI gets blocked
        SongView.ItemsSource = new List<Song>();
        if (response.IsSuccessStatusCode)
        {
            var content = await response.Content.ReadAsStringAsync();
            vm.Songs = await Task.Factory.StartNew(() =>
            {
                return JsonConvert.DeserializeObject<List<Song>>(content);
            });
        }

        SongView.ItemsSource = vm.Songs;
    }

And even with just this code it still blocks the UI on the same line.

private async void Button_Clicked(object sender, EventArgs e)
    {
        HttpClient client = new HttpClient();
        client.MaxResponseContentBufferSize = 256000;

        var uri = new Uri(string.Format("http://localhost:50715/api/values"));

        var response = await client.GetAsync(uri); // This is where UI gets blocked
    }

Can you point out what I'm doing wrong?