For those interested, It appears the reason was because of a compiler error I hit, and didn't ask about, or really worry how to resolve it. :-/ Function declaration: typedef boost::function < VSSP ( std::string, EncodingEnum) > CreateTypeFunc; bool ElementBase::disconnectCreateTypeSignal(const CreateTypeFunc& slot) { LOG4CXX_DEBUG(logger_, "disconnectCreateTypeSignal in"); bool retValue = false; createTypeSignal_.disconnect(slot); } Error: (apologies for the length) c:\Program Files\boost\boost_1_35_0\boost\signals\signal_template.hpp(242) : error C2666: 'boost::operator`=='' : 4 over loads have similar conversions; c:\Program Files\boost\boost_1_35_0\boost\function\function_base.hpp(669): could be 'boo st::enable_if_c::type boost::operator ==::slo t_fun ction_type>(Functor,const boost::function_base &) with [B=true,T=bool,R=boost::detail::function_traits_helpermodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::result_type,T 1=boost::detail::function_traits_helpermodel::VariantStorage (std::string,model:: EncodingEnum::EncodingEnum)>::type>::arg1_type,T2=boost::detail::functio n_traits_helpermodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::arg2_type,Combi ner=boost::last_valu emodel::VariantStorage (std::string,model:: EncodingEnum::EncodingEnum)>::type>::result_type>,Group=int,GroupCompare =std::less<int>,SlotFunction=boost::function,Functor=boost::signal2< boost::detail::funct ion_traits_helper (std::string,model::EncodingEnum::Encoding Enum)>::type>::result_type,boost::detail::function_traits_helper (std::string,model::EncodingEnum::EncodingEnum)>::type>::arg1_type,boost ::detail::function_traits_helpermodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::arg2_type,boo st::last_valuemodel::VariantStorage (std::s tring,model::EncodingEnum::EncodingEnum)>::type>::result_type>,int,std:: less<int>,boost::function>::slot_function_type]'; c:\Program Files\boost\boost_1_35_0\bo ost\function\function_base.hpp(660): or 'boost::enable_if_c::type boost::operator ==<Function>(const boost::f unction_base &,Functor) with [B=true,T=bool,Function=model::ElementBase::CreateTypeFunc,Functor=model ::ElementBase::Crea teTypeFunc]'; c:\Program Files\boost\boost_1_35_0\boost\function\function_template.hpp(832): or 'void boost::opera tor ==(const boost::function2 &,const boost::function2 &) with [R=model::VariantStorageSharedPtr,T0=std::string,T1=model::EncodingEnum: :EncodingEnum,Allocator=std::allocator<void>]'; or 'built-in C++ operator==(boost::function2::safe_bool with [R=model::VariantStorageSharedPtr, T0=std::string,T1=model::EncodingEnum::EncodingEnum,Allocator=std::alloc ator<void>], boost::function2 ::safe_bool with [R=model::VariantStorageSharedPtr,T0=std::string,T1=model::EncodingEnum: :EncodingEnum,Allocator=std::al locator<void>])'; while trying to match the argument list '(boost::signal2::slot_function_type with [R=boost::detail::function_traits_helper (std::string,model::EncodingEnum::EncodingEnum)>::type>::result_type,T1= boost::detail::function_traits_helper model::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::ar g1_type,T2=boost::detail::function_traits_helpermodel::VariantStorage (std::strin g,model::EncodingEnum::EncodingEnum)>::type>::arg2_type,Combiner=boost:: last_valuemodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::re sult_type>,Group=int,GroupCompare=std::less<int>,SlotFunction=boost::fun ction], const model::ElementBase::CreateTypeFunc)'; c:\Program Files\boost\boost_1_35_0\ boost\signals\signal_template.hpp(224) : see reference to function template instantiation 'void boost::signal2::do_disconnect<T>(const Function &,boost::mpl::bool_) with [R=boost::detail ::function_traits_helper (std::string,model::EncodingEnum::E ncodingEnum)>::type>::result_type,T1=boost::detail::function_traits_help er (std::string,model::EncodingEnum::EncodingEnum)>::type>::arg1_type,T2=bo ost::detail::function_traits_help ermodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>:: arg2_type,Combiner=boost::last_value (std::string,model::EncodingEnum::EncodingEnum)>::type>::result_type>,Gr oup=int,GroupCompare=std::less<in t>,SlotFunction=boost::function,T=model: :ElementBase::CreateTypeFunc,Function=model::ElementBase::CreateTypeFunc ,C_=false]' being compiled; c:\Documents and Set tings\td26134\Desktop\trunk1\src\model\ElementBase.cpp(440) : see reference to function template instantiation 'void boo st::signal2::disconnec tmodel::ElementBase::CreateTypeFunc(const T &) with [R=boost::detail::function_traits_helpermodel::VariantStorage (std::string, model::EncodingEnum::EncodingEnum)>::type>::result_type,T1=boost::detail ::function_traits_helpermodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::arg1_type,T2=bo ost::detail ::function_traits_helper (std::string,model::EncodingEnum::E ncodingEnum)>::type>::arg2_type,Combiner=boost::last_valuemodel::VariantStorage (std::string,model::EncodingEnum::EncodingEnum)>::type>::result_type>,Gr oup=int,Gro upCompare=std::less<int>,SlotFunction=boost::function,T=model::ElementBase::CreateTypeFunc]' being compiled scons: *** [build_dir\Windows\src-model\ElementBase.obj] Error 2