sftp and chroot question

I think I understand all of the moving parts of not allowing a chrooted user over sftp to write to their own home directory (/home/username), but instead to write to an enclosed directory (/home/username/hooray). I also understand that I can then use ForceCommand internal-sftp -d /hooray so the sftp user automatically arrives at and can write to the enclosed directory correctly. I've got all this set up and working fine.

Now, I'm supposed to interface with an ancient program that of course cannot be changed on the other end. They insist on using the command put /remotepath/filename /filename, instead of the obviously correct (and functional) put /remotepath/filename filename. They claim they can't do anything about this. I can't see an easy way out on my end. Suggestions? (Other than a large mallet...)