sequence statement does not trigger warning when mixed transaction rolls back

begin;

insert into t_1 values(3333);

select lastval(s_1) as "s_1's transaction start value";

+s_1's transaction start value

+2

insert into t_1 select next value for s_1;

...

rollback;

select lastval(s_1) as "s_1's actual value after rollback";

+s_1's actual value after rollback

+10

 rollback;

+Warnings:

+Warning        1196    Some non-transactional changed tables couldn't be rolled back