Hi, I have the exact same problem: http://boost.2283326.n4.nabble.com/ProgramOptions-explicit-empty-string-argu... --compression '' gave me a specified, empty compression switch value, as expected, on boost 1.58. However, on 1.59, the empty string counts against the positional arguments, and causes regressions. Also, --compression='' gives: The argument for option '--compression' should follow immediately after the equal sign. What is the recommended workaround? Is it planned to be fixed/changed? Thanks, Benedek