Percona-xtrabackup hot backup issue with MyIsam Engine

We are running with the MyIsam Engine and Percona-xtrabackup is throwing the following error as the inndb engine is skipped [ my.cnf skip-innodb]. How could I resolve this issue with out enabling the inndb engine?

percona-xtrabackup-2.0.0/bin:# ./innobackupex-1.5.1 --user="root" --password=*** --defaults-file="/etc/my.cnf" --socket=<path>/mysql.sock1  --ibbackup=<path>/percona-xtrabackup-2.0.0/bin/xtrabackup <path>/testbackup/

Percona Log :

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

IMPORTANT: Please check that the backup run completes successfully.
           At the end of a successful backup run innobackupex-1.5.1
           prints "completed OK!".

innobackupex-1.5.1: Using mysql  Ver 14.14 Distrib 5.1.57, for pc-linux-gnu (i686) using readline 5.1
innobackupex-1.5.1: Using mysql server version Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.

innobackupex-1.5.1: Created backup directory <path>/testbackup/2012-06-08_16-55-23
120608 16:55:23  innobackupex-1.5.1: Starting mysql with options:  --defaults-file='/etc/my.cnf' --password=xxxxxxxx --user='root' --socket='/data/mysql1/mysql.sock1' --unbuffered --
120608 16:55:23  innobackupex-1.5.1: Connected to database with mysql child process (pid=25611)
120608 16:55:25  innobackupex-1.5.1: Connection to database server closed

120608 16:55:25  innobackupex-1.5.1: Starting ibbackup with command: <path>/percona-xtrabackup-2.0.0/bin/xtrabackup  --defaults-file="/etc/my.cnf" --backup --suspend-at-end --target-dir=<path>/testbackup/2012-06-08_16-55-23
innobackupex-1.5.1: Waiting for ibbackup (pid=25618) to suspend
innobackupex-1.5.1: Suspend file '<path>/testbackup/2012-06-08_16-55-23/xtrabackup_suspended'

<path>/percona-xtrabackup-2.0.0/bin/xtrabackup version 2.0.0 for Percona Server 5.1.59 pc-linux-gnu (i686) (revision id: undefined)
xtrabackup: uses posix_fadvise().
xtrabackup: cd to /data/mysql1
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 = 5242880
InnoDB: The first specified data file ./ibdata1 did not exist:
InnoDB: a new database to be created!
120608 16:55:26  InnoDB: Setting file ./ibdata1 size to 10 MB
InnoDB: Database physically writes the file full: wait...
xtrabackup: Something wrong with source files...
innobackupex-1.5.1: Error: ibbackup child process has died at ./innobackupex-1.5.1 line 371.