Parsing bool type value

Hi all,

Taking a look at PostgreSQL HEAD today, I noticed that currently
PostgreSQL allows "of" value as bool type value.
So user can execute the following SQL.

=# SET enbale_seqscan TO of;

And I read the source code related to parsing bool value.
It compare TWO characters "off" and the setting value in
parse_bool_with_len() function.
Should we deny the "of" value as bool type value?

Regards,

-------
Sawada Masahiko