Hi, If I'm not mistaken, the current Slime version doesn't correctly parse in-package forms when the package name is a string or a keyword. This can be easily seen by writing in an edit buffer (in-package :foo) or (in-package "FOO") and then pressing C-c M-p (slime-repl-set-package) The following replacement correct this behaviour. (defun slime-search-buffer-package () (save-excursion (when (let ((case-fold-search t) (regexp "^(\\(cl:\\|common-lisp:\\)?in-package\\>[ \n\t\r':\"]*")) (or (re-search-backward regexp nil t) (re-search-forward regexp nil t))) (goto-char (match-end 0)) (let ((start (point))) (let ((pkg (ignore-errors (read (current-buffer))))) (and pkg (format "%S" pkg))))))) Best regards, António Leitão.