Why is my fake method called twice?

    
class Program
{
    static void Main(string[] args)
    {
        Program p = new Program();
        p.Test();
    }

    private static int doInsteadCalledCount = 0;
    public void Test()
    {
        MyClass mc = Isolate.Fake.Instance<MyClass>(Members.CallOriginal);
        Isolate.WhenCalled(() => mc.MyMethod(null)).
            DoInstead((callContext) =>
            {
                doInsteadCalledCount++;

                // Call the real instance method:
                MyParam p = callContext.Parameters[0] as MyParam;
                MyClass real = callContext.Instance as MyClass;

                MyResult result = real.MyMethod(p);
                return result;
            });
        Isolate.Swap.AllInstances<MyClass>().With(mc);

        MyClass myClass = new MyClass();
        MyParam myParam = new MyParam() { Value = "parameter value" };

        // Call "MyMethod". The fake method above gets called twice (?)
        MyResult myResult = myClass.MyMethod(myParam);
        MyResult myResult2 = myClass.MyOtherMethod(myParam);

        int count = doInsteadCalledCount;
    }

    private class MyClass
    {
        public MyResult MyMethod(MyParam p)
        {
            return new MyResult() { ResultValue = 1 };
        }
        public MyResult MyOtherMethod(MyParam p)
        {
            return new MyResult() { ResultValue = 2 };
        }
    }

    private class MyParam
    {
        public string Value
        {
            get; set;
        }
    }

    private class MyResult
    {
        public int ResultValue
        {
            get; set;
        }
    }
}