┌─[01:17:15]-[root@stavrovski]-[~]
└─› mkdir /tmp/another_test/ && for i in $(seq 1 20); do dd if=/dev/zero
of=/tmp/another_test/file-$i  bs=1024  count=10240 ; done

┌─[01:17:17]-[root@stavrovski]-[~]
└─› ls -1 /tmp/another_test/* | wc -l
20

┌─[01:17:36]-[root@stavrovski]-[~]
└─› du -csxh /tmp/another_test/*
0       total

┌─[01:28:19]-[root@stavrovski]-[~]
└─› du --version
du (GNU coreutils) 8.15
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Torbjörn Granlund, David MacKenzie, Paul Eggert,
and Jim Meyering.

┌─[01:39:04]-[root@stavrovski]-[~]
└─› cat /etc/issue
Arch Linux \r (\l)

┌─[01:39:22]-[root@stavrovski]-[~]
└─› pacman -Qs coreutils
local/coreutils 8.15-1 (base)

with coreutils-8.14 du is working as expected.

strace => http://pastebin.com/dPAKCNwF

-- 

An Educated Fool