upload file from stdin illegal seek

[gordon-to]

Trying to upload from stdin following the docs.

$ cat test.txt | rack files object upload --container database-backups --name test.txt --stdin content
error	seek /dev/stdin: illegal seek

upload works using filename

rack files object upload --container database-backups --name test.txt --file test.txt
Successfully uploaded object [test.txt] to container [database-backups]

version info:
rack version 1.2
commit: 09c14b0

OS info

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.4 LTS"