Error creating scheduled program

I am trying to create a scheduled program as follows: --
-- ONBS_STARTSQR  (Program)
--
BEGIN
  SYS.DBMS_SCHEDULER.CREATE_PROGRAM
    (
      program_name         => 'ONBS_STARTSQR',
      program_type         => 'EXECUTABLE',
      program_action       => '/prdfrm/onbs/onbs_sqr_rep.ksh -T',
      number_of_arguments  => 2,
      enabled              => FALSE,
      comments             => 'Script to run ONBS SQR reports.'
    );
  SYS.DBMS_SCHEDULER.DEFINE_PROGRAM_ARGUMENT
    (
      program_name         => 'ONBS_STARTSQR',
      argument_name        => '',
      argument_position    => 2,
      argument_type        => 'VARCHAR2',
      default_value        => '<NO VALUE>'
    );
  SYS.DBMS_SCHEDULER.ENABLE
    (name                  => 'ONBS_STARTSQR');
END;
/
------------------
I get the following error:
-----------------------------------------------------------------------------
Error at line 5
ORA-27453: is an invalid job or program argument name.