Trigger Fails

I am trying to create a trigger that will start sql trace when a certain user logs in. The trigger is created successfuly but the user is getting errors while logging in. This is what I get:

CDEV> CREATE OR REPLACE TRIGGER LogonTrigger AFTER LOGON ON NIGHTOPS.schema
2 BEGIN
3 dbms_session.SET_sql_trace(TRUE);
4 END;
5 /

Trigger created.

CDEV> connect nightops/password@sid
ERROR:
ORA-00604: error occurred at recursive SQL level 1
ORA-01031: insufficient privileges
ORA-06512: at "SYS.DBMS_SESSION", line 86
ORA-06512: at line 2

Warning: You are no longer connected to ORACLE.
CDEV>

Any help or other suggestions are appreciated.

the trigger owner needs direct grant of ALTER SESSION privilege

Thanks pando. Works great now!