Hi. I have exactly the same problem. Backup was generated with percona-xtrabackup 2.1.9, restored with 2.1.8-1. 

Log:
InnoDB: Doing recovery: scanned up to log sequence number 518996400128 (58%)
InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percent: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
InnoDB: Apply batch completed
InnoDB: Doing recovery: scanned up to log sequence number 519001643008 (66%)
InnoDB: Doing recovery: scanned up to log sequence number 519006885888 (75%)
InnoDB: Doing recovery: scanned up to log sequence number 519012128768 (83%)
InnoDB: Doing recovery: scanned up to log sequence number 519017371648 (91%)
InnoDB: Doing recovery: scanned up to log sequence number 519022509911 (99%)
2015-05-26 11:28:24 7f8027043780  InnoDB: Assertion failure in thread 140188387129216 in file page0cur.cc line 931
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.6/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
09:28:24 UTC - xtrabackup got signal 6 ;
This could be because you hit a bug or data is corrupted.
This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

Thread pointer: 0x2638eb0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x10000
xtrabackup(my_print_stacktrace+0x2e) [0x9351ce]
xtrabackup(handle_fatal_signal+0x262) [0x8f5e42]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x10340) [0x7f8026c25340]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x39) [0x7f8025389cc9]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7f802538d0d8]
xtrabackup(page_cur_parse_insert_rec(unsigned long, unsigned char*, unsigned char*, buf_block_t*, dict_index_t*, mtr_t*)+0x8d5) [0x9a8d05]
xtrabackup() [0x5c2b3c]
xtrabackup(recv_recover_page_func(unsigned long, buf_block_t*)+0x509) [0x5c46a9]
xtrabackup(buf_page_io_complete(buf_page_t*)+0x410) [0x6bdcf0]
xtrabackup(buf_read_page(unsigned long, unsigned long, unsigned long)+0x188) [0x69e6d8]
xtrabackup(buf_page_get_gen(unsigned long, unsigned long, unsigned long, unsigned long, buf_block_t*, unsigned long, char const*, unsigned long, mtr_t*)+0x230) [0x6badf0]
xtrabackup(ibuf_init_at_db_start()+0x2e5) [0x5eb3f5]
xtrabackup(dict_boot()+0x95f) [0x6b2a3f]
xtrabackup(innobase_start_or_create_for_mysql()+0x1604) [0x657ec4]
xtrabackup() [0x5910e9]
xtrabackup(main+0x1528) [0x57bc98]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7f8025374ec5]
xtrabackup() [0x58e7d6]

Please report a bug at https://bugs.launchpad.net/percona-xtrabackup
innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 2641.
        main::apply_log() called at /usr/bin/innobackupex line 1570
innobackupex: Error:
innobackupex: ibbackup failed at /usr/bin/innobackupex line 2641.