Faking Internal interfaces

The following code causes Typemock to fail.
internal interface IInternalInterface
{
List<string> SomeFunc(int someArg);
}

[TestClass, Isolated]
public class FakingInternalInterfaceTest
{
[TestMethod]
public void FakingInternalInterface()
{
var provider = Isolate.Fake.Instance<IInternalInterface>();
provider.SomeFunc(1);
}
}

Is faking internal interfaces not supported?