Remoting blocks when the slave disconnects during copying files

We are copying a big file from another job to the test job. That takes 4~5 minutes. The problem is, if the slave disconnects during this 4~5 minutes, the copy artifact doesn't know and doesn't stop. As a result, this job will run forever. Cancelling the job doesn't cancel it at this moment. Even disconnecting the slave doesn't stop the job. The only way out of this is restart the master, and I mean reboot the master machine, because soft restarting the Jenkins process will also hang during the restart. This is really ugly when it happens, so the priority is blocker.