[boost] [constrained-value] with 1.43.0

I found my code using constrained_value compiles with boost-1.42.0, but not with 1.43.0. Rather mysterious error message: /usr/local/src/boost.hg/boost/constrained_value/constrained.hpp:64: error: 'template<class ExceptionType> struct boost::constrained_value::throw_exception' is not a function, /usr/local/src/boost.hg/boost/throw_exception.hpp:74: error: conflict with 'template<class E> void boost::throw_exception(const E&)' /usr/local/src/boost.hg/boost/throw_exception.hpp:54: error: in call to 'throw_exception' scons: *** [mod/fixed_pt.os] Error 1