Can't add LUN's to the iscsi target specifying the bstype as "aio"

Issue

Trying to start tgtd with a target having a lun with backing store bstype as aio, fails with the following error.

#service tgtd start
Starting SCSI target daemon: [  OK  ]
tgtadm: invalid request
Command:
        tgtadm -C 0 --lld iscsi --op new --mode logicalunit --tid 1 --lun 1 -b /dev/vgdata/wcrepo01  --bstype aio 
exited with code: 22.