Why is Gradle able to mock final classes?

The Mockito documentation says that you can't mock a final class and yet running such a test through Gradle works. Specifically, I have an unit test in an Android project that has the following:

@Mock
private ViewTreeObserver mockTreeObserver;
...
@Before
public void setUp() {
    MockitoAnnotations.initMocks(this);
    ...
}

ViewTreeObserver is a final class.

I need to support a legacy development environment in Eclipse as well Android Studio. Studio and Gradle command-line using the wrapper both pass. Eclipse fails with

org.mockito.exceptions.base.MockitoException: 
Cannot mock/spy class android.view.ViewTreeObserver

As well as 'why?' I really need to know how to get Eclipse to pass if possible (without rewriting the test).

The various library versions are as follows:

• gradle-2.2.1 (wrapper used by Studio and command-line)


• mockito-core-1.9.5


• robolectric-2.4


• android-20 (unit test classpath configuration in Eclipse)