Problem in Verify.NonPublic on abstract protected meth

I have the following class:

public abstract class Command
{
   public Command()  { }
   public void Execute()
   {
       InnerExecute();
   }
   protected abstract void InnerExecute();
}

and The following test:

[TestMethod]
   public void Execute_StandardExecution_InnerExecuteWasCalled()
   {
       var fakeCommand = Isolate.Fake.Instance<Command>(Members.CallOriginal);
       fakeCommand.Execute();
       Isolate.Verify.NonPublic.WasCalled(fakeCommand,"InnerExecute");
   }

running this test result in:

Test method Crap4NetTests.BasicCommandTest.Execute_StandardExecution_InnerExecuteWasCalled threw exception: TypeMock.VerifyException:
TypeMock Verification: Method Mock0000Command.InnerExecute() was expected but was not called.

any idea why this is so?

:!: making InnerExecute public and using "regular" verify seems to work just fine