IntelliJ Iris code incomplete

I want to use a nice class diagram tool in IntelliJ CE. The code iris looks good to me, but it looks like it's incomplete: I have a class public class Child extends Parent implements SomeInterface

, all 3 in one package. The iris code will not show the relationship between the two classes. Any idea why?

Specifically:

import ...;
public class PointLight extends Light implements LimitedLight {
    //
}