In your .emacs you do it like this, so you can not just set the needed coding-system but also have it different depending on the lisp implmenetation used:
(require 'slime) (setf slime-lisp-implementations '((sbcl ("sbcl") :coding-system utf-8-unix) (clisp ("clisp") :coding-system utf-8-unix) (cmucl ("lisp") :coding-system iso-latin-1-unix))) (slime-setup)
-- Ignas Mikalajūnas