Compiling the following snippet in MSVC++ 6.5 + STLport 4.5.3 with the trunk #include <boost/lexical_cast.hpp> int main() { return 0; } results in ...\boost\detail\lcast_precision.hpp(79) : error C2027: use of undefined type 'STATIC_ASSERTION_FAILURE<0>' ...\boost\detail\lcast_precision.hpp(89) : see reference to class template instantiation 'boost::detail::lcast_precision<T>' being compiled [...] The offending asserion in boost/detail/lcast_precision.hpp is BOOST_STATIC_ASSERT(!is_specialized_bin || limits::digits + 0UL < ULONG_MAX / 30103UL && precision_bin > limits::digits10 + 0UL && precision_bin <= streamsize_max + 0UL ); This problem did not arise with Boost 1.34 because boost/lexical_cast.hpp did not use the newly created lcast_precision.hpp. Other assertions in lcast_precision<> seem to work OK, so looks like is this particular one that should be fixed only. I lack the skills to propose a patch myself, but I can locally try patches others may provide. Thank you, Joaquín M López Muñoz Telefónica, Investigación y Desarrollo