Compiling this code with gcc: #include <boost/config.hpp> #include <boost/mpl/apply.hpp> template < class MF, class T > struct myMF : boost::mpl::apply<MF,T> { BOOST_STATIC_CONSTANT(bool,value=type::value); }; int main() { return 0; } Gives: "gcc.compile.c++ ..\..\..\bin.v2\libs\tti\test\TestMFHasTypeMFC.test\gcc-mingw-4.5.2\debug\TestMFHasTypeMFC.o TestMFHasTypeMFC.cpp:18:5: error: 'type' has not been declared "g++" -ftemplate-depth-128 -O0 -fno-inline -Wall -pedantic -g -Wno-variadic-macros -I"..\..\.." -I"C:\Programming\VersionControl\boost" -c -o "..\..\..\bin.v2\libs\tti\test\TestMFHasTypeMFC.test\gcc-mingw-4.5.2\debug\TestMFHasTypeMFC.o" "TestMFHasTypeMFC.cpp"" MF is a metafunction with a boost::mpl::bool_ type. Since I am using apply using metafunction forwarding, why does gcc tell me that 'type' has not been declared ? Is this a bug in gcc or in my simple code above ? The error occurs with all flavors of gcc, but VC++ 8,9,10 gives no error.