JSON_TABLE: Column privilege is insufficient for query with json_table

drop database if exists db;

drop user if exists u@localhost;

create database db;

use db;

create table t (a text);

insert into t values ('{"foo":"bar"}');

create user u@localhost;

grant select (a) on db.t to u@localhost;

--connect (con1,localhost,u,,db)

select a from t;

select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;

MariaDB [db]> select * from t, json_table(t.a, '$' columns(f varchar(20) path '$.foo')) as jt;

ERROR 1142 (42000): SELECT command denied to user 'u'@'localhost' for table 'jt'