distcp / mv is not working on ftp

i'm just trying to backup some files to our ftp-server.

hadoop distcp hdfs:///data/ ftp://user:pass@server/data/

returns after some minutes with:

Task TASKID="task_201308231529_97700_m_000002" TASK_TYPE="MAP" TASK_STATUS="FAILED" FINISH_TIME="1380217916479" ERROR="java\.io\.IOException: Cannot rename parent(source): ftp://x:x@backup2/data/, parent(destination): ftp://x:x@backup2/data/
at org\.apache\.hadoop\.fs\.ftp\.FTPFileSystem\.rename(FTPFileSystem\.java:557)
at org\.apache\.hadoop\.fs\.ftp\.FTPFileSystem\.rename(FTPFileSystem\.java:522)
at org\.apache\.hadoop\.mapred\.FileOutputCommitter\.moveTaskOutputs(FileOutputCommitter\.java:154)
at org\.apache\.hadoop\.mapred\.FileOutputCommitter\.moveTaskOutputs(FileOutputCommitter\.java:172)
at org\.apache\.hadoop\.mapred\.FileOutputCommitter\.commitTask(FileOutputCommitter\.java:132)
at org\.apache\.hadoop\.mapred\.OutputCommitter\.commitTask(OutputCommitter\.java:221)
at org\.apache\.hadoop\.mapred\.Task\.commit(Task\.java:1000)
at org\.apache\.hadoop\.mapred\.Task\.done(Task\.java:870)
at org\.apache\.hadoop\.mapred\.MapTask\.run(MapTask\.java:329)
at org\.apache\.hadoop\.mapred\.Child$4\.run" TASK_ATTEMPT_ID="" .

I googled a bit and added

fs.ftp.host = backup2
fs.ftp.user.backup2 = user
fs.ftp.password.backup2 = password

to core-site.xml, then I was able to execute:

hadoop fs -ls ftp:///data/
hadoop fs -rm ftp:///data/test.file

but as soon as I try

hadoop fs -mv file:///data/test.file ftp:///data/test2.file
mv: `ftp:///data/test.file': Input/output error

I enabled debug-logging in our ftp-server and got:

Sep 27 15:24:33 backup2 ftpd[38241]: command: LIST /data
Sep 27 15:24:33 backup2 ftpd[38241]: <--- 150
Sep 27 15:24:33 backup2 ftpd[38241]: Opening BINARY mode data connection for '/bin/ls'.
Sep 27 15:24:33 backup2 ftpd[38241]: <--- 226
Sep 27 15:24:33 backup2 ftpd[38241]: Transfer complete.
Sep 27 15:24:33 backup2 ftpd[38241]: command: CWD ftp:/data
Sep 27 15:24:33 backup2 ftpd[38241]: <--- 550
Sep 27 15:24:33 backup2 ftpd[38241]: ftp:/data: No such file or directory.
Sep 27 15:24:33 backup2 ftpd[38241]: command: RNFR test.file
Sep 27 15:24:33 backup2 ftpd[38241]: <--- 550

looks like the generation of "CWD" is buggy, hadoop tries to cd into "ftp:/data", but should use "/data"