A friend of the instructor's was laid off several years ago by a small Silicon Valley consulting firm and, as part of the lay off paperwork, he was asked to sign an employment discrimination waiver in exchange for receipt of his final paycheck, but no additional severance payment was offered to the laid-off employee by the employer. On these facts, can you see a reason for why the waiver might be deemed invalid if the ex-employee decided to then sue the employer for employment discrimination?