Hello, I've just updated the trunk version of Boost (rev. 71184). Now GCC 4.6 fails to compile due to the following error: --- [error] --- boost-trunk/boost/serialization/version.hpp:57:17: error: conflicting declaration ‘int boost::serialization::version<T>::value’ boost-trunk/boost/serialization/version.hpp:52:5: error: ‘boost::serialization::version<T>::value’ has a previous declaration as ‘const int boost::serialization::version<T>::value’ boost-trunk/boost/serialization/version.hpp:57:17: error: declaration of ‘const int boost::serialization::version<T>::value’ outside of class is not definition [-fpermissive] --- [/error] --- It seems that adding the const specifier fixes the problem, that is: #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION template<class T> const int version<T>::value; #endif Could you fix it? Thank you very much! Best, -- Marco