I can't reproduce your crash. Also, I can't find a mcharset package. Here's what I did: (require 'emu-x20) (setq jis (mapconcat 'char-to-string '(?\^[ ?\$ ?B ?\$ ?\" ?\^[ ?\(?B) "")))) (setq euc (encode-mime-charset-string (decode-mime-charset-string jis 'iso-2022-jp) 'euc-jp)) (setq jiseuc (concat jis euc)) ;; fatal error (6) is happen at next line. (decode-mime-charset-string jiseuc 'automatic-conversion) This produced a string containing one kanji and 2 iso-8859-1 characters. Martin