Hello, I am using boost 1.37 and gcc 4.3.2. I am getting a very nasty error when I mix up boost headers and tr1 headers in one compilation unit. Here is my code: #include <functional> using namespace std; using namespace tr1; #include <boost/program_options.hpp> using namespace boost; void blub() { } function<void()> i1(blub); //error: expected constructor, destructor, or type conversion before '<' token std::function<void()> i2(blub); //Compiles fine tr1::function<void()> i3(blub); //Compiles fine boost::function<void()> i4(blub); //Compiles fine I did add the 'boost/tr1/tr1/' folder to the very beginning of global include list. What is wrong?