cbbackup/cbrestore doesn't backup and restore item flag correctly

I create one item on one node and restore it to another node. I use memcached client to check the item flag before and after backup/restore. The item flag mismatches.

Chishengs-MacBook-Pro:membase-cli chisheng$ ./cbbackup http://Administrator:password@10.5.2.22:8091 ~/backup/backup2
  [####################] 100.0% (1/1 msgs)
bucket: default, msgs transferred...
       : total | last | per sec
 batch : 4 | 4 | 81.5
 byte : 5 | 5 | 101.9
 msg : 1 | 1 | 20.4
done

Chishengs-MacBook-Pro:membase-cli chisheng$ ./cbrestore ~/backup/backup2 http://Administrator:password@10.5.2.23:8091 -x try_xwm=0
  [####################] 100.0% (1/1 msgs)
bucket: default, msgs transferred...
       : total | last | per sec
 batch : 1 | 1 | 15.7
 byte : 5 | 5 | 78.5
 msg : 1 | 1 | 15.7
done

The python output:
>>> c= MemcachedClient('10.5.2.22',11211)
>>> c.set("chisheng",0,0xfffffff0,"lindy")
(4288761800, 5038202653468618, '')
>>> c.get("chisheng")
(4294967280, 5038202653468618, 'lindy')
>>> a=MemcachedClient('10.5.2.23', 11211)
>>> a.get("chisheng")
(4043309055, 5039149778647819, 'lindy')

The first field is the item flag for the return value for get()