How to Mock instanceof in Mockito

I have a piece of code, what I want test with Mockito:

mockedClass instanceof SampleInterface

The mockedClass is mocked object whats type is a MockedClass , and the SampleInterface is an Interface. This is the failing point:

Validate.isTrue(mockedClass instanceof SampleInterface, "The mockedClass is not a SampleInterface");

How to mock this code?