lambda in a static method of an interface

[Remi Forax]

This code currently compiles but doesn't work at runtime

public interface User {
   public default String firstName() {
     return transform(0);
   }

   public default String lastName() {
     return transform(1);
   }

   public abstract String transform(int index);

   public static User User(String firstName, String lastName) {
     return ref -> (ref == 0)? firstName: lastName;
   }

   public static void main(String[] args) {
     User bob = User("Bob", "Vance");
     System.out.println(bob.firstName());
     System.out.println(bob.lastName());
   }
}

Exception in thread "main" java.lang.IncompatibleClassChangeError: Class 
java.lang.String does not implement the requested interface User
     at User$$Lambda$1.transform(Unknown Source)
     at User.firstName(User.java:3)
     at User$$Lambda$1.firstName(Unknown Source)
     at User.main(User.java:18)

I believe it's a bug in javac, the desugared method is not declared 
static but should:
   public java.lang.String lambda$0(java.lang.String, java.lang.String, 
int);

BTW, I use the b83 binary build, not the lastest mecurial tip.

cheers,
Rémi