KCL does not do vigerous type checking in interpreted mode for structure references. eg. (defstruct x a b) (defstruct y c d) (Setf xx (make-x)) (y-c xx) => Nil, not an error. (y-c 13) => an error, correct. This caused me some pain recently and I suspect that it could be a disaster if structure components are given and explicit type, eg. Char. Regards, Anthony.