Wrong result for LATERAL DERIVED join

--source include/have_innodb.inc

CREATE TABLE t1 (a varchar(35), b varchar(4)) ENGINE=InnoDB;

INSERT INTO t1 VALUES

('Albania','AXA'),('Australia','AUS'),('American Samoa','AMSA'),('Bahamas','BS');

CREATE TABLE t2 (a varchar(4), b varchar(50), PRIMARY KEY (b,a), KEY (a)) ENGINE=InnoDB;

INSERT INTO t2 VALUES

  ('BERM','African Methodist Episcopal'),

  ('AUS','Anglican'),('BERM','Anglican'),

  ('BS','Anglican'),

  ('BS','Baptist'),

  ('BS','Methodist'),

  ('BS','Protestant');

let query=

SELECT t1.a

FROM (SELECT a FROM t2 GROUP BY a ORDER BY COUNT(DISTINCT b) LIMIT 1) dt

JOIN t1 ON dt.a=t1.b;

--replace_column 9 #

eval EXPLAIN $query;

eval $query;

DROP TABLES t1, t2;