AAA syntax: struct not supported

    public struct MyStruct
    {
        public double FirstNumber
        { get; set; }
    }
        [Test, Isolated]
        public void SupportStruct()
        {
            MyStruct strtw = Isolate.Fake.Instance<MyStruct>(Members.ReturnRecursiveFakes);
            Isolate.WhenCalled(()=>strtw.FirstNumber).WillReturn(10);
        }

failed: TypeMock.TypeMockException : 
*** Can not create MockObject of struct, try using MockAll
   at TypeMock.MockManager.MockObject(Type type, Constructor mockConstructors, Object[] args)
   at TypeMock.MockManager.a(Type A_0, BindingFlags A_1)
   at TypeMock.MockManager.CreateRecursiveFake[T](BindingFlags flags)
   at cc.Instance[T](Members behavior)