WorkItem update from ZOS using CURL

Hello,

Im stuck when I try to update a RTC workitem from a Curl ZOS command (running trough the BPXBATSL program).
I try to follow : https://jazz.net/wiki/bin/view/Main/ResourceOrientedWorkItemAPIv2#Examples

Here are my steps :

1) signon :

PGM /usr/lpp/ported/bin/curl
-v -k -L -c /tmp/cookies.txt
https://xx.xx.xxx.xx:9443/jazz/authenticated/identity

PGM /usr/lpp/ported/bin/curl
-v -k -L -b /tmp/cookies.txt -c /tmp/cookies.txt
-d j_username=toto -d j_password=toto
https://xx.xx.xxx.xx:9443/jazz/j_security_check

2) get the workitem in xml format

PGM /usr/lpp/ported/bin/curl
-v -k -L -b /tmp/cookies.txt -c /tmp/cookies.txt
-H "Accept:application/x-oslc-cm-change-request+xml"
-H "Content-Type:application/x-oslc-cm-change-request+xml"
https://xx.xx.xxx.xx:9443/jazz/oslc/workitems/3584.xml?oslc_cm.properties=dc:essai

3) put the workitem

PGM /usr/lpp/ported/bin/curl
-D - -k -v -L -b /tmp/cookies.txt
-H "accept:application/x-oslc-cm-change-request+xml"
-H "Content-Type:application/x-oslc-cm-change-request+xml"
-X PUT
-d /SYSTEM/tmp/toto.xml
https://xx.xx.xxx.xx:9443/jazz/oslc/workitems/3584.xml?oslc_cm.properties=dc:essai

When I ran the PUT, the workitem is not updated at all.
The user defined property essai has the value not assigned (even if there was another value before)
It seems to me that all data in the file toto.xml are ignored.
I try the same put with the firefox addon for REST and it worked.

Any ideas ?

Thanks.