[Chimera-users] Using addaa at the N-terminus?

Hi, I read in the manual that addaa can be used at the N-terminus. I'm not having any luck doing this. I've been assigning the amino acid to add at the N-term with a lower number, like: addaa cys,5,alpha :6.a The error message says 'Can only add to last residue'. Is there something I may be doing wrong? Thanks, Tosan