Structural most specific fails when method reference is passed to overloaded method

This program fails to compile:

import java.util.*;
import java.util.stream.*;

class MostSpecific08 {
    
    static class C {
        int getInt() { return -1; }
        Integer getInteger() { return -1; }
    }
    
    void testMref(Stream<C> sp) {
        IntStream si_p = sp.map(C::getInt);
        Stream<Integer> si_r = sp.map(C::getInteger);
    }
    
    void testLambda(Stream<C> sp) {
        IntStream si_p = sp.map(c->c.getInt());
        Stream<Integer> si_r = sp.map(c->c.getInteger());
    }
}

class Test {
    void g(IntFunc i) { }
    void g(RefFunc i) { }

    void test() {
        g(Person::getAge);
    }
}