password in pg_shadow

Is all in next example good? See:

abil=> CREATE USER myname WITH PASSWORD BuBuBuBu;
CREATE USER                            ^^^^^^^^^^ 

abil=> select * from pg_shadow;
usename |usesysid|usecreatedb|usetrace|usesuper|usecatupd|passwd     |valuntil
myname  |    5808|f          |f       |f       |f        |bubububu   |
      ^^^^^^^^ 
 
(4 rows)


Why is in pg_shadow.passwd low case only?
                        Zakkr