How to audit trigger enabling/disabling

Hello,

(8.1.7.4 on SUN Solaris 8, know it's a bit old but that's not the point
;)

This is a question about how to use the AUDIT statement to keep track of the enabling/disabling of triggers.

I set the AUDIT_TRAIL to TRUE and issue the following statement (logged as SYSDBA) :
AUDIT TRIGGER BY ACCESS; Then, I issued this statement :
alter trigger <owner>.<trigger> disable;

When I check the sys.aud$ table, I can't see any audit row for that statement.
(On the other side, I have some tables audited by access for delete,
insert and update statements. These statements log audit when issued)

I'm a bit confused with the AUDIT syntax and I surely forgot something. Thank you in advance for any help you can provide.

Cheers

-- 
SL