diff --git a/enum.h b/enum.h
index 6618a7a..c3eee79 100644
--- a/enum.h
+++ b/enum.h
@@ -949,16 +949,6 @@ operator >>(std::basic_istream<Char, Traits>& stream, Enum &value)             \
         stream.setstate(std::basic_istream<Char, Traits>::failbit);            \
                                                                                \
     return stream;                                                             \
-}                                                                              \
-                                                                               \
-namespace std {                                                                \
-template <> struct hash<Enum>                                                  \
-{                                                                              \
-   size_t operator()(const Enum &x) const                                      \
-   {                                                                           \
-      return std::hash<size_t>()(x._to_index());                               \
-   }                                                                           \
-};                                                                             \
 }
 
 
@@ -1293,4 +1283,17 @@ BETTER_ENUMS_CONSTEXPR_ map<Enum, T> make_map(T (*f)(Enum))
 
 }
 
+#ifndef BETTER_ENUMS_DECLARE_STD_HASH
+#define BETTER_ENUMS_DECLARE_STD_HASH(type) \
+	namespace std { \
+		template <> struct hash<type> \
+		{ \
+			size_t operator()(const type &x) const \
+			{ \
+				return std::hash<size_t>()(x._to_index()); \
+			} \
+		}; \
+	}	
+#endif
+
 #endif // #ifndef BETTER_ENUMS_ENUM_H