which method should be synchronized in delegation pattern in Java

In delegation pattern, if I have a concrete class and a wrapper class:

class Wrapper {
    Concrete concrete = new Concrete();
    void fn() {
        concrete.fn();
    }
}

class Concrete {
    void fn() {
        ...
    }
}

If the method fn() should be synchronized, then where should I put the synchronized keyword? If we assume Concrete::fn() will only be called by Wrapper::fn(), is it true that either place is fine?

Thanks!