Views and default values

Hello.

I have a problem (one more ;) with views, rules for inserting and default
values.

Data Base:

create table foo (
cod serial primary key,
explication text,
silly bool default 't');

create view v_foo as
select * from foo;

create rule v_foo_ins as on insert to v_foo do instead
insert into foo values (
NEW.cod,
NEW.explication,
NEW.silly);

What is my problem with this?... It is easy to make insert in 'foo' with
default value:

# insert into foo(explication) values ('Because is in love');

But, what about 'v_foo'? If I make:

# insert into v_foo(explication) values ('Because have not slept');

I don't get default values properly because insert rule is forcing null
values. In fact, in this example I don't get nothing except an error for
trying to insert null value in primary key field.

Is there any way of resolving this problem?. Perhaps NEW might pass a
'default' value when it doesn't receive any data? have I lost some
important concept?...

Thanks.

David