Editing a Test Case title using cmd

Hi, when I try to edit a test case using 

im editissue --field=Title="My Title" idxx (where idxx is my test case id) I receive the following error 

Could not save modified item idxx: MKS124079: The field "Title" is not a valid field in the Type "Test Case".

Using " im viewissue idxx " -> can see that field Title is there.

How to make it work ?

I tried updating the title manually (from gui) and it works, but still cannot use im editissue (....) and it's important for scripting.