存储过程报错

Oracle 9的OEM中编辑一个行级的删除前的存储过程begin
  delete from t_employee where t_employee.dep_id =:old.dep_id;
end;编译时抱错
行号= 0 列号=0  错误文本=pl/sql:compliateion unit analysis teminated
行号= 2 列号=42 错误文本=pls-00553:?????????如果改成
begin
  delete from t_employee where t_employee.dep_id ='0001';
end;
则不会抱错,
按理delete from t_employee where t_employee.dep_id =:old.dep_id;是没有什么错误的.
请指教,在线等待