in support.c

        if (! in_string && c == '\\' && *file->bptr == '\n'
                && in_define        /* '\\''\n' is deleted in #define line, */
                    /*   provided the '\\' is not the 2nd byte of mbchar.   */
                && ! last_is_mbchar( file->buffer, strlen( file->buffer) - 2
                && ! keep_spaces) // this parenthesis should be the end of the previous line
            ) {