btrbk on a GPT multi partition BTRFS drive

Hello
I am running Debian Bullseye on a nvme drive on my laptop that is partitioned as follow (i shortened the names for convenience):
/dev/nvme0 EFI
/dev/nvme1 /boot
/dev/nvme5 /
/dev/nvme7 /home
/dev/nvme3 swap

Nvme3-5-7 are all encrypted with Luks.
Inside the partition I have created subvolumes and installed my system inside them.

/dev/nvme5 has subvol @ for the root and subvol @root-snapshot for the snapshots
/dev/nvme7 has subvol @home for home and sub @home-snapshot

Both the snapshot subvol are mounted via fstab as /root-snapshot and /home-snaptshot

My config file for btrbk is:

Code:timestamp_format long
snapshot_preserve_min 5d
snapshot_preserve 30d

volume /dev/mapper/nvme0n1p5_crypt
snapshot_dir root-snapshot
subvolume @

volume /dev/mapper/nvme0n1p7_crypt
snapshot_dir home-snapshot
subvolume @homebut this doesn't work..

Could someone help in setting this correctly?
I tried to add a target option

Code:target /dev/mapper/nvme0n1p5_crypt/to indicate that the snapshot should be created inside that volume but I get an ambiguous target configuration..

Anybody could help me in finding what is wrong?
Thanks