select returns null for information_schema.statistics.collation field

create table test.some_table (field1 int unsigned not null, field2 varchar(64), primary key (field1), key(field2));

/* collation with their correct value */

select * from information_schema.STATISTICS where table_name='some_table' and table_schema='test';

/* collation is null here */

select table_schema, table_name, index_name, column_name, collation

from information_schema.STATISTICS

where table_schema='test' and table_name='some_table';

/* collation (quoted) is null here */

select table_schema, table_name, index_name, column_name, `collation`

from information_schema.STATISTICS

where table_schema='test' and table_name='some_table';