btrbk fails if "volume" is "/" about btrbk HOT 10 CLOSED

btrbk command line client, version 0.16  (Tue Apr 28 22:38:40 2015)
WARNING: Skipping subvolume section: Subvolume "@home" not present in btrfs subvolume list for "/"
Completed within: 0s  (Tue Apr 28 22:38:40 2015)
--------------------------------------------------------------------------------
Backup Summary (btrbk command line client, version 0.16)

Date:   Tue Apr 28 22:38:40 2015
Config: /foo/bar/btrbk.conf

Legend:
+++  created subvolume (source snapshot)
---  deleted subvolume (source snapshot)
***  received subvolume (non-incremental)
>>>  received subvolume (incremental)
--------------------------------------------------------------------------------
//@home
!!! Subvolume "@home" aborted: Subvolume "@home" not present in btrfs subvolume list for "/"

NOTE: Some errors occurred, which may result in missing backups!
Please check warning and error messages above.

NOTE: Dryrun was active, none of the operations above were actually executed!

die("subvolume info not present: $sroot/$svol") unless($svol_node);

btrbk command line client, version 0.17.0  (Thu May  7 23:30:14 2015)
Using configuration: /foo/bar//btrbk.conf
WARNING: Skipping subvolume "//@home": Failed to fetch subvolume detail
Completed within: 0s  (Thu May  7 23:30:14 2015)
--------------------------------------------------------------------------------
Backup Summary (btrbk command line client, version 0.17.0)

    Date:   Thu May  7 23:30:14 2015
    Config: /foo/bar/btrbk.conf

Legend:
    +++  created subvolume (source snapshot)
    ---  deleted subvolume
    ***  received subvolume (non-incremental)
    >>>  received subvolume (incremental)
--------------------------------------------------------------------------------
//@home
!!! Subvolume "//@home" aborted: Failed to fetch subvolume detail

NOTE: Some errors occurred, which may result in missing backups!
Please check warning and error messages above.

NOTE: Dryrun was active, none of the operations above were actually executed!

snapshot_create_always yes
volume /
  subvolume @home

# cat /tmp/btrfs.conf
snapshot_create_always yes
volume /
  subvolume @home

# btrfs sub create /\@home
Create subvolume '//@home'
# btrbk -c /tmp/btrbk.conf dryrun
--------------------------------------------------------------------------------
Backup Summary (btrbk command line client, version 0.17.0)

    Date:   Fri May  8 12:42:30 2015
    Config: /tmp/btrbk.conf

Legend:
    +++  created subvolume (source snapshot)
    ---  deleted subvolume
    ***  received subvolume (non-incremental)
    >>>  received subvolume (incremental)
--------------------------------------------------------------------------------
//@home
+++ ///@home.20150508

volume /
  subvolume /