HI, the following code gives a compile error on VC10 and GCC 4.2.1. Clang and GCC 4.7 like it: #include <boost/fusion/sequence.hpp> #include <boost/fusion/include/define_struct_inline.hpp> #include <iostream> template<class T> struct enclosing { BOOST_FUSION_DEFINE_STRUCT_INLINE( employee, (std::string, name) (int, age)) }; int main() { enclosing<int>::employee e; e.name="abc"; std::cout<<boost::fusion::deref(boost::fusion::begin(e)); } complete error mssag on VC10: 1>c:\program files (x86)\boost\boost_1_51\boost\fusion\iterator\deref.hpp(34): error C2504: 'enclosing<T>::employee::employee_iterator<boost_fusion_uglified_Seq,N>::deref<boost_fusion_uglified_T>': Basisklasse undefiniert 1> with 1> [ 1> T=int, 1> boost_fusion_uglified_Seq=enclosing<int>::employee, 1> N=0 1> ] 1> and 1> [ 1> boost_fusion_uglified_T=enclosing<int>::employee::employee_iterator<enclosing<int>::employee,0> 1> ] 1> c:\program files (x86)\boost\boost_1_51\boost\fusion\iterator\deref.hpp(53): Siehe Verweis auf die Instanziierung der gerade kompilierten Klassen-template "boost::fusion::extension::deref_impl<boost::fusion::iterator_facade_tag>::apply<Iterator>". 1> with 1> [ 1> Iterator=enclosing<int>::employee::employee_iterator<enclosing<int>::employee,0> 1> ] 1> c:\users\ulfi\documents\visual studio 2010\projects\test\test\test.cpp(18): Siehe Verweis auf die Instanziierung der gerade kompilierten Klassen-template "boost::fusion::result_of::deref<Iterator>". 1> with 1> [ 1> Iterator=enclosing<int>::employee::employee_iterator<enclosing<int>::employee,0> 1> ] 1>c:\users\ulfi\documents\visual studio 2010\projects\test\test\test.cpp(18): error C2893: Funktionsvorlage 'result_of::deref<Iterator>::type boost::fusion::deref(const Iterator &)' konnte nicht spezialisiert werden 1> Mit den folgenden Vorlagenargumenten: 1> 'enclosing<T>::employee::employee_iterator<boost_fusion_uglified_Seq,N>' 1> with 1> [ 1> T=int, 1> boost_fusion_uglified_Seq=enclosing<int>::employee, 1> N=0 1> ] I don't have a clue what is wrong here. Is the error on my side? i just added the template<class T> to the example code of BOOST_FUSION_DEFINE_STRUCT_INLINE. Without, everything is fine. Gretings, Oswin