Hi Alessio, You implemented the user-extensible sequence protocol. Did you by any chance change the type of Sequence from BUILT-IN-CLASS to SLOT-CLASS? If so, I have a little bit of a negative interaction with my METACLASS changes. Nothing that can't be fixed; I'll probably need to study AMOP for the solution, but I was just wondering. Does crhodes specify the new class of SEQUENCE in his protocol? Should we switch it to STANDARD-CLASS? Bye, Erik.