[boost] program-options thread problem

I have both added current program-options to my boost build tree, and all the usual variants of libboost_program_options-gcc.a, also libboost_python-gcc-mt.a. Linking against libboost_program_options-gcc.a I get errors about pthread symbols. Adding -pthread fixes it. It looks to me that libboost_program_options-gcc.a is referencing pthread symbols. nm /usr/local/src/boost_1_31_0.gcc34/stage/lib/libboost_program_options-gcc.a | grep thread U pthread_mutex_destroy U pthread_mutex_init w pthread_mutex_lock w pthread_mutex_unlock w pthread_mutex_lock w pthread_mutex_unlock Yup,sure is.