diff --git a/toml/traits.hpp b/toml/traits.hpp
index 6a347e8..aec49b0 100644
--- a/toml/traits.hpp
+++ b/toml/traits.hpp
@@ -2,6 +2,7 @@
 #define TOML11_TRAITS
 #include <type_traits>
 #include <utility>
+#include <chrono>
 #include <tuple>
 
 namespace toml
@@ -85,6 +86,10 @@ template<typename T> struct is_std_tuple : std::false_type{};
 template<typename ... Ts>
 struct is_std_tuple<std::tuple<Ts...>> : std::true_type{};
 
+template<typename T> struct is_chrono_duration: std::false_type{};
+template<typename Rep, typename Period>
+struct is_chrono_duration<std::chrono::duration<Rep, Period>>: std::true_type{};
+
 // to use toml::get<std::tuple<T1, T2, ...>> in C++11
 template<std::size_t ... Ns> struct index_sequence{};
 
diff --git a/toml/types.hpp b/toml/types.hpp
index fb16075..0e9637d 100644
--- a/toml/types.hpp
+++ b/toml/types.hpp
@@ -82,9 +82,6 @@ inline std::basic_string<charT, traits, alloc> stringize(value_t t)
 
 namespace detail
 {
-template<typename T> struct is_chrono_duration: std::false_type{};
-template<typename Rep, typename Period>
-struct is_chrono_duration<std::chrono::duration<Rep, Period>>: std::true_type{};
 
 template<typename T>
 constexpr inline value_t check_type()