Add spare to MDADM Raid array

[Gr0m1t]

I had a raid array running with 5 scsi drives & 1 spare drive.
Long story short, it got messed up and I lost the spare and one other drive.
I ran mdadm /dev/md0 --add /dev/sdf1
& it added the drive and now I have 5 disks in my array and it is clean. When I try to add the 6th spare drive it says out of space. Is there a special option to tell mdadm to add it as a spare?