Delete rule does not prevent truncate

Hi,

I very much hope this is an accidental bug rather than a deliberate feature !

PostgreSQL 9.4.4

create rule no_auditupd as on update to app_security.app_audit do
instead nothing;
create rule no_auditdel as on delete to app_security.app_audit do
instead nothing;

\d+ app_security.app_audit
<snip>
Rules:
no_auditdel AS
ON DELETE TO app_security.app_audit DO INSTEAD NOTHING
no_auditupd AS
ON UPDATE TO app_security.app_audit DO INSTEAD NOTHING

The truncate trashes the whole table ;-(

According to the FabulousManual(TM) :
event : The event is one of SELECT, INSERT, UPDATE, or DELETE.

Thus I can't create a rule to "do nothing" on truncates, thus I am stuck !