NHibernate更新未更改的记录

从数据库检索记录列表:

using(UnitOfWork.Start())
{
   queuedJobs = aJobServiceManager.GetAllJobs().Where(aJob => aJob.Status == PricingStatus.QUEUED).ToList();
}

/* Do some work on the record*/
using(UnitOfWork.Start())
{
   //aJob is a record from queuedJobs.
   aJobServiceManager.Save(aJob);
   //When Flush is called I'm expecting only aJob to be updated in the database.
   //aJob is correctly updated BUT
   //All the other records in queuedJobs are also updated (their version field is incremented).
   UnitOfWork.Current.Flush();
}

为什么nHibernate要在所有记录都没有更改的情况下更新它们?如何停止这种行为?