I have a Trigger that will fire whenever any DDL statement is executed.Below the trigger code

Code:
create or replace trigger
   DDLTrigger
AFTER DDL ON DATABASE
BEGIN
insert into
   perfstat.stats$ddl_log
(
   user_name,
   ddl_date,
   ddl_type,
   object_type,
   owner,
   object_name
)
VALUES
(
   ora_login_user,
   sysdate,
   ora_sysevent,
   ora_dict_obj_type,
   ora_dict_obj_owner,
   ora_dict_obj_name
);
END;
When i m testing this trigger by truncating a table i m getting ORA-ERROR as
"ora-04098 trigger is invalid and failed re-validation"

How should i solve this issue ?