I was playing with program_options in svn trunk after recent fixes for multitoken options and hit an assertion failure with the attached example. The example takes two options - one multitoken and one positional, and simply outputs provided values. The two invocations below work OK: $ bin/gcc-4.2.2/debug/multitoken_positional some_file -m token1 token2 File: some_file Multitoken: token1 token2 $ bin/gcc-4.2.2/debug/multitoken_positional -m token1 token2 --file some_file File: some_file Multitoken: token1 token2 While experimenting with this one asserts: $ bin/gcc-4.2.2/debug/multitoken_positional -m token1 token2 -- some_file multitoken_positional: ../../../../../svn_boost/trunk/libs/program_options/src/cmdline.cpp:295: std::vector > boost::program_options::detail::cmdline::run(): Assertion `opt2.original_tokens.size() == 1' failed. Aborted Should an exception be thrown instead, or this is a use-case worth to support? Thanks, Gevorg