redmine 1.2.1.stable, create an issue on REST problem

hello,
I have a problem. i'm trying to create an issue, but api says to me:

<?xml version="1.0" encoding="UTF-8"?>
<errors>
  <error>Subject can't be blank</error>
</errors>

my posts request body is:

<?xml version="1.0"?>
  <issue>
    <subject>example issue</subject>
    <description>my content</description>
  </issue>
</xml>

url is:

what's wrong?

Redmine