Mocking getClass()

In Java I want to write test for method (simplified snippet):

public class MyClass {
    private static final Set<Class> SOME_SET = new HashSet<Class>(Arrays.asList(Foo.class, Bar.class));

    public boolean isValid(Class clazz){
        return SOME_SET.contains(clazz);
    }
}

The problem with following test

import static org.mockito.Mockito.when;
import org.mockito.Mockito;

public class MyClassTest {
    @Test
    public void isValid_Foo_returnsTrue(){
        Foo foo = Mockito.mock(Foo.class);
        MyClass target = new MyClass();
        assertTrue(target.isValid(foo));
   }
}

is that on mocked class Foo, foo.getClass() returns the class name with additional suffix. Something like this:

Foo$$EnhancerByMockitoWithCGLIB$$45508b12

Because of this reason test fails because SOME_SET.contains(clazz) returns false.

I was unable to mock getClass() method on Foo:

Mockito.when(foo.getClass()).thenReturn(Foo.class);

Because compiler was complaining: The method thenReturn(Class<capture#1-of ? extends Foo>) in the type OngoingStubbing<Class<capture#1-of ? extends Foo>> is not applicable for the arguments (Class<Foo>)

The question is, how to achieve that getClass() method of mocked object returns same value as getClass() method on real(non mocked) object?