xb 2.1 against ps 5.6 gives Error: Tablespace is not sensible during backup

While running XtraBackup 2.1 (revno 609) against Percona Server 5.6 via PTB with RQG load, backup fails:

Backup - starting: full backup cycle=0 incremental backup cycle=0
Backup - options: --parallel=3
Backup - path: /data/bin/ps-5.6/bin:/data/bin/ps-5.6/libexec:/data/bin/xb-2.1-xtradb56
Backup - command: innobackupex --defaults-file=/data/dev/var/test-95/mysql.1/my.cnf --no-timestamp --tmpdir=/data/dev/var/test-95 --parallel=3

InnoDB Backup Utility v1.5.1-xtrabackup; Copyright 2003, 2009 Innobase Oy
and Percona Ireland Ltd 2009-2012. All Rights Reserved.

This software is published under
the GNU GENERAL PUBLIC LICENSE Version 2, June 1991.

130601 06:13:41 innobackupex: Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_file=/data/dev/var/test-95/mysql.1/my.cnf;mysql_read_default_group=xtrabackup' (using password: NO).
130601 06:13:41 innobackupex: Connected to MySQL server
IMPORTANT: Please check that the backup run completes successfully.
           At the end of a successful backup run innobackupex
           prints "completed OK!".

innobackupex: Using mysql server version 5.6.11

innobackupex: Created backup directory /data/dev/var/test-95/backup-0.0

130601 06:13:41 innobackupex: Starting ibbackup with command: xtrabackup_56 --defaults-file="/data/dev/var/test-95/mysql.1/my.cnf" --defaults-group="mysqld" --backup --suspend-at-end --target-dir=/data/dev/var/test-95/backup-0.0 --tmpdir=/data/dev/var/test-95 --parallel=3
innobackupex: Waiting for ibbackup (pid=20681) to suspend
innobackupex: Suspend file '/data/dev/var/test-95/backup-0.0/xtrabackup_suspended_2'

xtrabackup_56 version 2.1.3 for MySQL server 5.6.10 Linux (x86_64) (revision id: undefined)
xtrabackup: uses posix_fadvise().
xtrabackup: cd to /data/dev/var/test-95/mysql.1/data
xtrabackup: Target instance is assumed as followings.
xtrabackup: innodb_data_home_dir = ./
xtrabackup: innodb_data_file_path = ibdata1:10M:autoextend
xtrabackup: innodb_log_group_home_dir = ./
xtrabackup: innodb_log_files_in_group = 2
xtrabackup: innodb_log_file_size = 536870912
xtrabackup: using O_DIRECT
InnoDB: Allocated tablespace 6, old maximum was 0
 InnoDB: Error: Tablespace is not sensible; Table: rqg1/table100_innodb_compressed Space ID: 0 Filepath: ./rqg1/table100_innodb_compressed.ibd
2013-06-01 06:13:41 7fe2594da7e0 InnoDB: Operating system error number 2 in a file operation.
InnoDB: The error means the system cannot find the path specified.
InnoDB: Error: could not open single-table tablespace file ./rqg1/table100_innodb_compressed.ibd
InnoDB: We do not continue the crash recovery, because the table may become
InnoDB: corrupt if we cannot apply the log records in the InnoDB log to it.
InnoDB: To fix the problem and start mysqld:
InnoDB: 1) If there is a permission problem in the file and mysqld cannot
InnoDB: open the file, you should modify the permissions.
InnoDB: 2) If the table is not needed, or you can restore it from a backup,
InnoDB: then you can remove the .ibd file, and InnoDB will do a normal
InnoDB: crash recovery and ignore that table.
InnoDB: 3) If the file system or the disk is broken, and you cannot remove
InnoDB: the .ibd file, you can set innodb_force_recovery > 0 in my.cnf
InnoDB: and force InnoDB to continue crash recovery here.
innobackupex: Error: ibbackup child process has died at /data/bin/xb-2.1-xtradb56/innobackupex line 391.
Backup - completed: time 1 full backup cycle=0 incremental backup cycle=0 rc=3