Get RULE condition and commands

What is the proper way of getting RULE condition and commands? The query below does not work.

select pg_get_expr(ev_qual, ev_class, true) as condition,
       pg_get_expr(ev_action, ev_class, true) as commands
from pg_rewrite;

ERROR:  bogus varno: 2

********** Error **********

ERROR: bogus varno: 2
SQL state: XX000