(length (string-split (string #\a (integer->char 255) #\b)
                          (integer->char 255)))
    => 1

where I think it should be 2.

        * srfi-13.c (scm_string_split): Compare char/char in scan.  Mixing an
        unsigned int SCM_CHAR and a char string meant an 8-bit char was never
        matched.