Project Server 2013 PSI calls from Sharepoint 2013

Hello,

I'm migrating code from 2010 to 2013.

I have a user control that I deploy in Sharepoint that calls the PSI. In 2010 it was working well. Now in 2013 and Claims authentication, I always get: "The HTTP request is unauthorized with client authentication scheme 'Ntlm'. The authentication header received from the server was 'NTLM,Negotiate'." when I call any PSI (even GetCurrentUserUid) with any user (even the project admin).

It looks like the credentials aren't passed to the PSI and it calls them as anonymous. Anyone can help ?

Thanks