incorrect result returned with binary protocol (prepared statements)

create table  DUPPP (code varchar(10) primary key);

INSERT INTO DUPPP(code) VALUES ('LINE1'), ('LINE2'), ('LINE3');

SELECT X.* FROM (SELECT CODE, RN FROM (SELECT A.CODE, @cnt := @cnt + 1 AS RN FROM  DUPPP A, (SELECT @cnt := 0) C) T) X;

drop table DUPP;

CODE	RN

LINE1	1

LINE2	2

LINE3	3

CODE	RN

LINE3	3

LINE3	3

LINE3	3