Confusing compiler warning

Main.java

import java.util.List;

public class Main {
    public static void main(String[] args) {

        Foo foo = new Foo();
        // Why does the compiler complain about an unchecked assignment, because foo is raw?
        List<Integer> numbers = foo.getNumbers();
    }

    public static class Foo<T> {

        public T getValue() {
            return null;
        }


        public List<Integer> getNumbers() {
            return null;
        }
    }
}

The problem is more noticeable during annotation processing when the return type for getNumbers is a list without type arguments.