diff --git a/example/interface_example.cpp b/example/interface_example.cpp
index d874f47..3164e61 100644
--- a/example/interface_example.cpp
+++ b/example/interface_example.cpp
@@ -12,7 +12,7 @@ See interface.hpp in this directory for details.
 #include <callable_traits/config.hpp>
 #ifdef CALLABLE_TRAITS_MSVC
 int main(){ return 0; }
-#elif defined CALLABLE_TRAITS_GCC_OLDER_THAN_4_9_2
+#elif defined CALLABLE_TRAITS_GCC_OLDER_THAN_5_0_0
 int main(){ return 0; }
 #else
 
diff --git a/include/callable_traits/add_member_const.hpp b/include/callable_traits/add_member_const.hpp
index 3656496..fa6d74a 100644
--- a/include/callable_traits/add_member_const.hpp
+++ b/include/callable_traits/add_member_const.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_member_const_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_member_const<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct add_member_const {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::add_member_const,
-            detail::add_member_const_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/add_member_cv.hpp b/include/callable_traits/add_member_cv.hpp
index 76f87d6..317958d 100644
--- a/include/callable_traits/add_member_cv.hpp
+++ b/include/callable_traits/add_member_cv.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_member_cv_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_member_cv<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct add_member_cv {
 
         using type = detail::fail_if_invalid<
-        typename detail::traits<T>::add_member_cv,
-        detail::add_member_cv_error<true>>;
+            typename detail::traits<T>::add_member_cv,
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/add_member_lvalue_reference.hpp b/include/callable_traits/add_member_lvalue_reference.hpp
index 15a3790..a5cca91 100644
--- a/include/callable_traits/add_member_lvalue_reference.hpp
+++ b/include/callable_traits/add_member_lvalue_reference.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_member_lvalue_reference_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_member_lvalue_reference<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct add_member_lvalue_reference {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::add_member_lvalue_reference,
-            detail::add_member_lvalue_reference_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/add_member_rvalue_reference.hpp b/include/callable_traits/add_member_rvalue_reference.hpp
index 84df857..53741a5 100644
--- a/include/callable_traits/add_member_rvalue_reference.hpp
+++ b/include/callable_traits/add_member_rvalue_reference.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_member_rvalue_reference_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_member_rvalue_reference<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct add_member_rvalue_reference {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::add_member_rvalue_reference,
-            detail::add_member_rvalue_reference_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/add_member_volatile.hpp b/include/callable_traits/add_member_volatile.hpp
index 13573be..d372e07 100644
--- a/include/callable_traits/add_member_volatile.hpp
+++ b/include/callable_traits/add_member_volatile.hpp
@@ -15,23 +15,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_member_volatile_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_member_volatile<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct add_member_volatile {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::add_member_volatile,
-            detail::add_member_volatile_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/add_varargs.hpp b/include/callable_traits/add_varargs.hpp
index ffe948e..efca9b6 100644
--- a/include/callable_traits/add_varargs.hpp
+++ b/include/callable_traits/add_varargs.hpp
@@ -14,25 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct add_varargs_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::add_varargs<T> is not "
-                "a meaningful operation for this T. T must "
-                "be a function, function pointer, function "
-                "reference, or member function pointer.");
-        };
-    }
-
     template<typename T>
     struct add_varargs {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::add_varargs,
-            detail::add_varargs_error<true>>;
+            varargs_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/apply_return.hpp b/include/callable_traits/apply_return.hpp
index adf2e36..7142d85 100644
--- a/include/callable_traits/apply_return.hpp
+++ b/include/callable_traits/apply_return.hpp
@@ -16,14 +16,6 @@ namespace callable_traits {
 
     namespace detail {
 
-        template<bool Sfinae>
-        struct apply_return_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::apply_return<T, R> is "
-                "not a meaningful operation for this T.");
-        };
-
         template<typename T, typename R>
         struct apply_return_helper {
             using type = typename detail::traits<T>::template apply_return<R>;
@@ -36,12 +28,18 @@ namespace callable_traits {
         };
     }
 
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(apply_return)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(apply_return,
+    invalid_types_for_apply_return)
+
+
     template<typename T, typename R>
     struct apply_return {
 
         using type = detail::fail_if_invalid<
             typename detail::apply_return_helper<T, R>::type,
-            detail::apply_return_error<true>>;
+            invalid_types_for_apply_return>;
     };
 
     template<typename T, typename R>
diff --git a/include/callable_traits/arg_at.hpp b/include/callable_traits/arg_at.hpp
index aa894c5..46531f6 100644
--- a/include/callable_traits/arg_at.hpp
+++ b/include/callable_traits/arg_at.hpp
@@ -15,21 +15,29 @@ Distributed under the Boost Software License, Version 1.0.
 #include <tuple>
 
 namespace callable_traits {
-    
-    namespace detail {
-        struct arg_at_error : sfinae_error {};
-    }
 
     template<std::size_t I, typename T>
     struct arg_at {
 
-        using type = detail::fail_if_invalid<
-            detail::weak_at<I, typename detail::traits<T>::arg_types>,
-            detail::arg_at_error>;
+        private:
+
+            using arg_types = typename args<T>::type;
+
+        public:
+
+        // SFINAEs away if index is out of range or if argument
+        // types cannot be determined. Simple error messages are
+        // provided in case the error occurs outside of a SFINAE context
+
+        using type = detail::sfinae_try<
+
+            detail::at<I, arg_types>,
+
+            detail::fail_if<I >= std::tuple_size<arg_types>::value,
+                index_out_of_range_for_parameter_list>
+        >;
     };
 
-    // returns callable_traits::invalid_type if
-    // index is out of range
     template<std::size_t I, typename T>
     using arg_at_t = typename arg_at<I, T>::type;
 }
diff --git a/include/callable_traits/args.hpp b/include/callable_traits/args.hpp
index cae250d..eaaa1ad 100644
--- a/include/callable_traits/args.hpp
+++ b/include/callable_traits/args.hpp
@@ -14,26 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct args_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "Could not determine the parameters for "
-                "T in callable_traits::args<T>. Note: "
-                "If T is the type of a generic lambda or "
-                " overloaded/templated function object, "
-                "the parameters cannot be determined. ");
-        };
-    }
-
     template<typename T>
     struct args {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::arg_types,
-            detail::args_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/clear_args.hpp b/include/callable_traits/clear_args.hpp
index c9be9d6..bce90d2 100644
--- a/include/callable_traits/clear_args.hpp
+++ b/include/callable_traits/clear_args.hpp
@@ -14,23 +14,17 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(clear_args)
 
-        template<bool Sfinae>
-        struct clear_args_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::clear_args<T> is "
-                "not a meaningful operation for this T.");
-        };
-    }
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(clear_args,
+        cannot_clear_the_parameter_list_for_this_type)
 
     template<typename T>
     struct clear_args {
 
         using type = detail::fail_if_invalid<
         typename detail::traits<T>::clear_args,
-        detail::clear_args_error<true>>;
+        cannot_clear_the_parameter_list_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/config.hpp b/include/callable_traits/config.hpp
index 866d2fc..00c0769 100644
--- a/include/callable_traits/config.hpp
+++ b/include/callable_traits/config.hpp
@@ -14,16 +14,21 @@ Distributed under the Boost Software License, Version 1.0.
 
  #ifndef __clang__
   #if defined __GNUC__
+
    #define CALLABLE_TRAITS_GCC
-   #if __GNUC__ >= 6
-    #define CALLABLE_TRAITS_GCC_AT_LEAST_4_9_2
-   #elif __GNUC__ >= 5
+
+   #if __GNUC__ < 5
+     #define CALLABLE_TRAITS_GCC_OLDER_THAN_5_0_0
+   #endif
+
+   #if __GNUC__ >= 5
     #define CALLABLE_TRAITS_GCC_AT_LEAST_4_9_2
    #elif __GNUC__ == 4 && __GNUC_MINOR__ == 9 && __GNUC_PATCHLEVEL__ >= 2
     #define CALLABLE_TRAITS_GCC_AT_LEAST_4_9_2
    #else
     #define CALLABLE_TRAITS_GCC_OLDER_THAN_4_9_2
-   #endif //#if __GNUC__ >= 6
+   #endif //#if __GNUC__ >= 5
+
   #endif //#if defined __GNUC__
  #endif //#ifndef __clang__
 
diff --git a/include/callable_traits/copy_qualifiers.hpp b/include/callable_traits/copy_qualifiers.hpp
index 65b22f9..57c5144 100644
--- a/include/callable_traits/copy_qualifiers.hpp
+++ b/include/callable_traits/copy_qualifiers.hpp
@@ -15,15 +15,10 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(copy_qualifiers)
 
-        template<bool Sfinae>
-        struct copy_qualifiers_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "TODO: error message for callable_traits::copy_qualifiers");
-        };
-    }
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(copy_qualifiers,
+        cannot_copy_qualifiers_for_these_types)
 
     template<typename To, typename From>
     struct copy_qualifiers {
@@ -31,7 +26,7 @@ namespace callable_traits {
         using type = detail::fail_if_invalid<
             typename detail::copy_qualifiers_impl<
                 detail::traits<To>, detail::traits<From>>::type,
-            detail::copy_qualifiers_error<true>>;
+            cannot_copy_qualifiers_for_these_types>;
     };
 
     template<typename To, typename From>
diff --git a/include/callable_traits/detail/core.hpp b/include/callable_traits/detail/core.hpp
index f684c2a..2aee925 100644
--- a/include/callable_traits/detail/core.hpp
+++ b/include/callable_traits/detail/core.hpp
@@ -10,8 +10,8 @@ Distributed under the Boost Software License, Version 1.0.
 #ifndef CALLABLE_TRAITS_DETAIL_CORE_HPP
 #define CALLABLE_TRAITS_DETAIL_CORE_HPP
 
-#include <callable_traits/detail/traits.hpp>
 #include <callable_traits/detail/utility.hpp>
+#include <callable_traits/detail/traits.hpp>
 #include <callable_traits/detail/function_object.hpp>
 #include <callable_traits/detail/function.hpp>
 #include <callable_traits/detail/pmf.hpp>
diff --git a/include/callable_traits/detail/function_object.hpp b/include/callable_traits/detail/function_object.hpp
index dfa4c97..2ddba17 100644
--- a/include/callable_traits/detail/function_object.hpp
+++ b/include/callable_traits/detail/function_object.hpp
@@ -44,7 +44,7 @@ namespace callable_traits {
 
             using is_member_pointer = std::false_type;
             using is_member_function_pointer = std::false_type;
-            using remove_member_pointer = type;
+            using remove_member_pointer = invalid_type;
             using remove_varargs = invalid_type;
             using add_varargs = invalid_type;
             using clear_args = invalid_type;
diff --git a/include/callable_traits/detail/sfinae_errors.hpp b/include/callable_traits/detail/sfinae_errors.hpp
new file mode 100644
index 0000000..4d877c5
--- /dev/null
+++ b/include/callable_traits/detail/sfinae_errors.hpp
@@ -0,0 +1,91 @@
+/*!
+@copyright Barrett Adair 2016
+
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+
+*/
+
+#ifndef CALLABLE_TRAITS_SFINAE_ERRORS_HPP
+#define CALLABLE_TRAITS_SFINAE_ERRORS_HPP
+
+#include <callable_traits/config.hpp>
+#include <type_traits>
+
+namespace callable_traits {
+
+    namespace detail {
+
+        struct sfinae_error{};
+
+        template<typename T>
+        struct success {
+            static constexpr bool value = true;
+            struct _ { using type = T; };
+        };
+    
+        template<bool B, typename T>
+        struct fail_if : T {
+
+            static_assert(std::is_base_of<sfinae_error, T>::value,
+                "incorrect usage of fail_if");
+
+            static constexpr bool value = B;
+        };
+
+        template<typename T, typename... ThrowIfs>
+        using sfinae_try = typename CALLABLE_TRAITS_DISJUNCTION(
+            ThrowIfs...,
+            success<T>
+        )::_::type;
+    }
+
+#define CALLABLE_TRAITS_PP_CAT_(x, y) x ## y
+#define CALLABLE_TRAITS_PP_CAT(x, y) CALLABLE_TRAITS_PP_CAT_(x, y)
+
+#define CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(origin)     \
+namespace callable_traits_ERROR {                              \
+    template<typename ErrorMessage>                            \
+    struct origin :                                            \
+        ::callable_traits::detail::sfinae_error                \
+        { struct _ {}; };                                      \
+}                                                              \
+/**/
+
+#define CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(origin, name)    \
+struct CALLABLE_TRAITS_PP_CAT(name, _ ){};                       \
+struct name : callable_traits_ERROR::origin<                     \
+    CALLABLE_TRAITS_PP_CAT(name, _ )>{};                         \
+/**/
+
+    /*** parameter manipulation errors ***/
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(parameters)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(parameters,
+        index_out_of_range_for_parameter_list)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(parameters,
+        cannot_determine_parameters_for_this_type)
+
+
+    /*** parent class errors ***/
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(parent_class)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(parent_class,
+        type_is_not_a_member_pointer)
+
+
+    /*** member qualifier errors ***/
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(member_qualifiers)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(member_qualifiers,
+        member_qualifiers_are_illegal_for_this_type)
+
+
+    /*** varargs errors ***/
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(varargs)
+
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(varargs,
+        varargs_are_illegal_for_this_type)
+}
+#endif // #ifndef CALLABLE_TRAITS_SFINAE_ERRORS_HPP
diff --git a/include/callable_traits/detail/unguarded/args_pack_manipulations.hpp b/include/callable_traits/detail/unguarded/args_pack_manipulations.hpp
index d9616d7..54ec63b 100644
--- a/include/callable_traits/detail/unguarded/args_pack_manipulations.hpp
+++ b/include/callable_traits/detail/unguarded/args_pack_manipulations.hpp
@@ -28,14 +28,14 @@ struct insert_impl;
 template<std::size_t... I, typename... U, std::size_t StartTo>
 struct insert_impl<CALLABLE_TRAITS_IX_SEQ(I...), std::tuple<U...>, StartTo> {
 
-    static_assert(StartTo <= arg_count, "Insert index out of range");
-
-    using type =
+    using type = sfinae_try<
         CALLABLE_TRAITS_BEGIN_PACK_MANIP
         typename std::tuple_element<
             map_insert<I, arg_count, StartTo, sizeof...(U)>::value,
             std::tuple<CALLABLE_TRAITS_ARGS_PACK..., U...>>::type...
-        CALLABLE_TRAITS_END_PACK_MANIP;
+        CALLABLE_TRAITS_END_PACK_MANIP,
+
+    >;
 };
 
 template<std::size_t N, typename... U>
@@ -58,15 +58,14 @@ struct remove_impl;
 template<std::size_t... Is, std::size_t Index, std::size_t Count>
 struct remove_impl<CALLABLE_TRAITS_IX_SEQ(Is...), Index, Count> {
 
-    static_assert(Index < arg_count,
-        "Remove index out of range");
-
-    using type =
+    using type = sfinae_try<
         CALLABLE_TRAITS_BEGIN_PACK_MANIP
         typename std::tuple_element<
         map_remove<Is, Index, Count>::value,
         std::tuple<CALLABLE_TRAITS_ARGS_PACK...>>::type...
-        CALLABLE_TRAITS_END_PACK_MANIP;
+        CALLABLE_TRAITS_END_PACK_MANIP,
+
+    >;
 };
 
 //when not removing anything
@@ -100,14 +99,14 @@ struct overwrite_impl;
 template<std::size_t... I, typename... U, std::size_t StartTo>
 struct overwrite_impl<CALLABLE_TRAITS_IX_SEQ(I...), std::tuple<U...>, StartTo> {
 
-    static_assert(StartTo <= arg_count, "Insert index out of range");
-
-    using type =
+    using type = sfinae_try<
         CALLABLE_TRAITS_BEGIN_PACK_MANIP
         typename std::tuple_element<
         map_overwrite<I, arg_count, StartTo, sizeof...(U)>::value,
         std::tuple<CALLABLE_TRAITS_ARGS_PACK..., U...>>::type...
-        CALLABLE_TRAITS_END_PACK_MANIP;
+        CALLABLE_TRAITS_END_PACK_MANIP,
+
+    >;
 };
 
 template<std::size_t StartIndex, typename... U>
diff --git a/include/callable_traits/detail/unguarded/function.hpp b/include/callable_traits/detail/unguarded/function.hpp
index f5fd23c..a6ba621 100644
--- a/include/callable_traits/detail/unguarded/function.hpp
+++ b/include/callable_traits/detail/unguarded/function.hpp
@@ -25,6 +25,7 @@ struct function<Return(Args...) CALLABLE_TRAITS_INCLUDE_QUALIFIERS>
     using remove_varargs = type;
     using add_varargs = Return (Args..., ...) CALLABLE_TRAITS_INCLUDE_QUALIFIERS;
     
+    // todo is this really necessary?
     using has_member_qualifiers_function = bool_type<
         !std::is_same<qualified_function_type, function_type>::value>;
         
diff --git a/include/callable_traits/detail/utility.hpp b/include/callable_traits/detail/utility.hpp
index c5d1c37..12ab497 100644
--- a/include/callable_traits/detail/utility.hpp
+++ b/include/callable_traits/detail/utility.hpp
@@ -10,6 +10,7 @@ Distributed under the Boost Software License, Version 1.0.
 #ifndef CALLABLE_TRAITS_DETAIL_UTILITY_HPP
 #define CALLABLE_TRAITS_DETAIL_UTILITY_HPP
 
+#include <callable_traits/detail/sfinae_errors.hpp>
 #include <callable_traits/config.hpp>
 #include <type_traits>
 #include <tuple>
@@ -35,29 +36,6 @@ namespace callable_traits {
         template<std::size_t I, typename Tup>
         using at = typename std::tuple_element<I, Tup>::type;
 
-
-        namespace util_detail {
-
-            template<std::size_t I, typename Tup, typename = std::true_type>
-            struct weak_at_t {
-                using type = at<I, Tup>;
-            };
-
-            template<std::size_t I, typename Tup>
-            struct weak_at_t<I, Tup, bool_type<I >= std::tuple_size<Tup>::value>>{
-                using type = invalid_type;
-            };
-
-            template<std::size_t I>
-            struct weak_at_t<I, invalid_type, std::true_type>{
-                using type = invalid_type;
-            };
-        }
-
-        // bounds-checked version of at (see above)
-        template<std::size_t I, typename Tup>
-        using weak_at = typename util_detail::weak_at_t<I, Tup>::type;
-
         // a faster version of std::decay_t
         template<typename T>
         using shallow_decay = typename std::remove_cv<
@@ -105,10 +83,6 @@ namespace callable_traits {
         using remove_member_pointer =
             typename util_detail::remove_member_pointer_t<T>::type;
 
-        struct sfinae_error {
-            struct _ {};
-        };
-
         namespace util_detail {
             template<typename T, bool Value>
             struct type_value {
@@ -120,11 +94,9 @@ namespace callable_traits {
             };
         }
 
-        template<typename T, typename FailType>
-        using fail_if_invalid = typename CALLABLE_TRAITS_DISJUNCTION(
-            util_detail::type_value<T, !std::is_same<T, invalid_type>::value>,
-            FailType
-        )::_::type;
+        template<typename T, typename ErrorType>
+        using fail_if_invalid = sfinae_try<T,
+            fail_if<std::is_same<T, invalid_type>::value, ErrorType>>;
 
         template<typename T, typename Fallback>
         using fallback_if_invalid = typename std::conditional<
diff --git a/include/callable_traits/expand_args.hpp b/include/callable_traits/expand_args.hpp
index ea3fde4..8db3b7f 100644
--- a/include/callable_traits/expand_args.hpp
+++ b/include/callable_traits/expand_args.hpp
@@ -14,22 +14,17 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(expand_args)
 
-        template<bool Sfinae>
-        struct expand_args_error {
-
-            static_assert(Sfinae,
-                "callable_traits::expand_args<T, U> is not a valid operation.");
-        };
-    }
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(expand_args,
+        cannot_expand_the_parameter_list_of_first_template_argument)
 
     template<typename T, template<class...> class Container>
     struct expand_args {
 
         using type = detail::fail_if_invalid<
         typename detail::traits<T>::template expand_args<Container>,
-        detail::expand_args_error<true>>;
+        cannot_expand_the_parameter_list_of_first_template_argument>;
     };
 
     template<typename T, template<class...> class Container>
diff --git a/include/callable_traits/insert_args.hpp b/include/callable_traits/insert_args.hpp
index ed39725..f0a2d32 100644
--- a/include/callable_traits/insert_args.hpp
+++ b/include/callable_traits/insert_args.hpp
@@ -14,22 +14,11 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct insert_args_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<std::size_t Index, typename T, typename... Args>
     struct insert_args {
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template insert_args<Index, Args...>,
-            detail::insert_args_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<std::size_t Index, typename T, typename... Args>
diff --git a/include/callable_traits/parent_class_of.hpp b/include/callable_traits/parent_class_of.hpp
index 73d0a4a..1aa233d 100644
--- a/include/callable_traits/parent_class_of.hpp
+++ b/include/callable_traits/parent_class_of.hpp
@@ -14,22 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct parent_class_of_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "TODO: error message for callable_traits::parent_class_of");
-        };
-    }
-
     template<typename T>
     struct parent_class_of {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::class_type,
-            detail::parent_class_of_error<true>>;
+            type_is_not_a_member_pointer>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/pop_back.hpp b/include/callable_traits/pop_back.hpp
index a68ada0..c3b860f 100644
--- a/include/callable_traits/pop_back.hpp
+++ b/include/callable_traits/pop_back.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct args_pop_back_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::args_push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T, std::size_t Count = 1>
     struct args_pop_back {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template pop_back<Count>,
-            detail::args_pop_back_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<typename T, std::size_t Count = 1>
diff --git a/include/callable_traits/pop_front.hpp b/include/callable_traits/pop_front.hpp
index acafffe..a37ac78 100644
--- a/include/callable_traits/pop_front.hpp
+++ b/include/callable_traits/pop_front.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct args_pop_front_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T, std::size_t Count = 1>
     struct args_pop_front {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template pop_front<Count>,
-            detail::args_pop_front_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
 
diff --git a/include/callable_traits/push_back.hpp b/include/callable_traits/push_back.hpp
index 271c968..c410b73 100644
--- a/include/callable_traits/push_back.hpp
+++ b/include/callable_traits/push_back.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct args_push_back_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T, typename... Args>
     struct args_push_back {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template push_back<Args...>,
-            detail::args_push_back_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<typename T, typename... Args>
diff --git a/include/callable_traits/push_front.hpp b/include/callable_traits/push_front.hpp
index 55c2cd7..19f7941 100644
--- a/include/callable_traits/push_front.hpp
+++ b/include/callable_traits/push_front.hpp
@@ -30,7 +30,7 @@ namespace callable_traits {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template push_front<Args...>,
-            detail::args_push_front_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<typename T, typename... Args>
diff --git a/include/callable_traits/qualified_parent_class_of.hpp b/include/callable_traits/qualified_parent_class_of.hpp
index 6b2eed6..8909f49 100644
--- a/include/callable_traits/qualified_parent_class_of.hpp
+++ b/include/callable_traits/qualified_parent_class_of.hpp
@@ -14,22 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct qualified_parent_class_of_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "TODO: error message for callable_traits::qualified_parent_class_of");
-        };
-    }
-
     template<typename T>
     struct qualified_parent_class_of {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::invoke_type,
-            detail::qualified_parent_class_of_error<true>>;
+            type_is_not_a_member_pointer>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/remove_args.hpp b/include/callable_traits/remove_args.hpp
index 8ddb37a..ec5f906 100644
--- a/include/callable_traits/remove_args.hpp
+++ b/include/callable_traits/remove_args.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct remove_args_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<std::size_t Index, typename T, std::size_t Count = 1>
     struct remove_args {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::template remove_args<Index, Count>,
-            detail::remove_args_error<true>>;
+            cannot_determine_parameters_for_this_type>;
     };
 
     template<std::size_t Index, typename T, std::size_t Count = 1>
diff --git a/include/callable_traits/remove_member_const.hpp b/include/callable_traits/remove_member_const.hpp
index 83e61b4..0a9ae4d 100644
--- a/include/callable_traits/remove_member_const.hpp
+++ b/include/callable_traits/remove_member_const.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct remove_member_const_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::remove_member_const<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct remove_member_const {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::remove_member_const,
-            detail::remove_member_const_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/remove_member_cv.hpp b/include/callable_traits/remove_member_cv.hpp
index b883c92..a717cbe 100644
--- a/include/callable_traits/remove_member_cv.hpp
+++ b/include/callable_traits/remove_member_cv.hpp
@@ -15,23 +15,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct remove_member_cv_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::remove_member_cv<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct remove_member_cv {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::remove_member_cv,
-            detail::remove_member_cv_error<true>>;
+            member_qualifiers_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/remove_member_pointer.hpp b/include/callable_traits/remove_member_pointer.hpp
index 6301fac..27ca87f 100644
--- a/include/callable_traits/remove_member_pointer.hpp
+++ b/include/callable_traits/remove_member_pointer.hpp
@@ -14,23 +14,17 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(remove_member_pointer)
 
-        template<bool Sfinae>
-        struct remove_member_pointer_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::remove_member_pointer<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(remove_member_pointer,
+        cannot_remove_member_pointer_from_this_type)
 
     template<typename T>
     struct remove_member_pointer {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::remove_member_pointer,
-            detail::remove_member_pointer_error<true>>;
+            cannot_remove_member_pointer_from_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/remove_varargs.hpp b/include/callable_traits/remove_varargs.hpp
index 822fb05..145240a 100644
--- a/include/callable_traits/remove_varargs.hpp
+++ b/include/callable_traits/remove_varargs.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct remove_varargs_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::remove_varargs<T> "
-                "is not a meaningful operation for this T.");
-        };
-    }
-
     template<typename T>
     struct remove_varargs {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::remove_varargs,
-            detail::remove_varargs_error<true>>;
+            varargs_are_illegal_for_this_type>;
     };
 
     template<typename T>
diff --git a/include/callable_traits/replace_args.hpp b/include/callable_traits/replace_args.hpp
index d3273b7..f12bd13 100644
--- a/include/callable_traits/replace_args.hpp
+++ b/include/callable_traits/replace_args.hpp
@@ -14,23 +14,12 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
-
-        template<bool Sfinae>
-        struct replace_args_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::push_back<T, Args...> is "
-                "not a meaningful operation for this T.");
-        };
-    }
-
     template<std::size_t Index, typename T, typename... Args>
     struct replace_args {
 
         using type = detail::fail_if_invalid<
         typename detail::traits<T>::template replace_args<Index, Args...>,
-        detail::replace_args_error<true>>;
+        cannot_determine_parameters_for_this_type>;
     };
 
     template<std::size_t Index, typename T, typename... Args>
diff --git a/include/callable_traits/result_of.hpp b/include/callable_traits/result_of.hpp
index 3fe7c4d..fd914a4 100644
--- a/include/callable_traits/result_of.hpp
+++ b/include/callable_traits/result_of.hpp
@@ -14,23 +14,17 @@ Distributed under the Boost Software License, Version 1.0.
 
 namespace callable_traits {
 
-    namespace detail {
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_ORIGIN(result_of)
 
-        template<bool Sfinae>
-        struct result_of_error : sfinae_error {
-
-            static_assert(Sfinae,
-                "callable_traits::result_of<T> is not "
-                "a meaningful operation for this T.");
-        };
-    }
+    CALLABLE_TRAITS_DEFINE_SFINAE_ERROR_FOR(result_of,
+        unable_to_determine_return_type)
 
     template<typename T>
     struct result_of {
 
         using type = detail::fail_if_invalid<
             typename detail::traits<T>::return_type,
-            detail::result_of_error<true>>;
+            unable_to_determine_return_type>;
     };
 
     template<typename T>
diff --git a/test/detail/args_pack_manipulations.cpp b/test/detail/args_pack_manipulations.cpp
index 499b732..41b9a15 100644
--- a/test/detail/args_pack_manipulations.cpp
+++ b/test/detail/args_pack_manipulations.cpp
@@ -2,6 +2,7 @@
 #include <utility>
 #include <type_traits>
 #include <callable_traits/config.hpp>
+#include <callable_traits/detail/sfinae_errors.hpp>
 
 #ifndef CT_ASSERT
 #define CT_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)