myisampack returns error when trying to compress a table with index on persistent column

test/t2.MYI gave error 138 on open

let $MYSQLD_DATADIR= `select @@datadir`;

CREATE TABLE t1 (DATA varchar(10000), d1 VARCHAR(40) AS (substring(DATA,1,40)) persistent, KEY (d1) )engine=myisam;

INSERT INTO t1 (data) VALUES (NULL),(repeat('a',1000)),('abcabs'),(repeat('b',1000));

flush table t1;

--exec $MYISAMPACK -sf $MYSQLD_DATADIR/test/t1

--exec $MYISAMCHK -srnq $MYSQLD_DATADIR/test/t1

check table t1;

checksum table t1;

drop table t1;