Android Unit Test giving not mocked message for a Mockito stubbed method

I've created the following test method where I mock Settings.Secure and stub the getString method of that class.

@Test
public void testIsDevicePostOwner() throws Exception {
    String mockDeviceId = "2c3977ad-0867-49d6-aad8-c2762f373551";

    Post mockedPost = mock(Post.class);

    Settings.Secure mockedSecure = mock(Settings.Secure.class);

    ContentResolver mockContentResolver = mock(ContentResolver.class);

    when(mockedSecure.getString(mockContentResolver, Settings.Secure.ANDROID_ID)).thenReturn(mockDeviceId);
}

When I run the test I get the following error:

java.lang.RuntimeException: Method getString in android.provider.Settings$Secure not mocked.

Does anybody have any ideas?