Very simple example:

#include <string>
#include <boost/program_options.hpp>

namespace po = boost::program_options;

int main(int argc, char* argv[])
{
    po::options_description recipients("Recipient(s)");
    recipients.add_options()
        ("csv",         po::value<std::string>(),     ""  )
        ("csv_name",    po::value<unsigned>(),        ""  )
    ;

    po::options_description cmdline_options;
    cmdline_options.add(recipients);

    po::variables_map vm;
    po::store(po::command_line_parser(argc, argv).options(cmdline_options).run(), vm);
    po::notify(vm);

    return 0;
}

And some tests:

>Test --csv test
in option 'csv_name': invalid option value

>Test --csv_name test
in option 'csv_name': invalid option value

>Test --csv_name 0

>Test --csv text
in option 'csv_name': invalid option value

>Test --csv 0

>Test --csv_name 0

>Test --csv_name 0 --csv text
multiple occurrences

Looks like that boost::program_option threats parameter "csv" as "csv_name".
Is it a feature or bug?