Flurl: 4.6.1 class library unit test "MissingMethodException"

To recreate:

1. Create a new .NetStandard library with a method using Flurl (EDIT: Not necessary, skip to step 2).
2. Create a class library targeting 4.6.1
3. Create project.json with the following

{
  "dependencies": {
    "FluentAssertions": "4.17.0",
    "Flurl": "2.2.1",
    "Flurl.Http": "1.1.1",
    "NSubstitute": "1.10.0",
    "xunit": "2.1.0"
  },
  "frameworks": {
    "net461": {}
  },
  "runtimes": {
    "win": {}
  }
}

1. Reload project
2. Try to run the following

[Fact]
public void Test()
{
    using (var x = new HttpTest())
    {
        "G".GetJsonAsync();
    }
}

Exception :

System.MissingMethodException Method not found: ‘System.Threading.Tasks.Task`1<System.Object> Flurl.Http.HttpExtensions.GetJsonAsync(System.String, System.Threading.CancellationToken, System.Net.Http.HttpCompletionOption)’. at Tests.Class1.Test()