Moq issue with many observers

gistfile1.txt

public interface IMakeStuff : IObserver<int>, IObserver<string>, IObserver<bool> { }

public class Tests
{
  [Fact]
  public void SimpleTest()
  {
    var maker = new Mock<IMakeStuff>()
    
    // Exception here
    var obj = maker.Object;
  }
}