diff --git a/include/tins/ip_address.h b/include/tins/ip_address.h
index e16387c..8b9b249 100644
--- a/include/tins/ip_address.h
+++ b/include/tins/ip_address.h
@@ -35,6 +35,7 @@
 #include <stdint.h>
 #include "cxxstd.h"
 #include "macros.h"
+#include <functional>
 
 namespace Tins {
 /**
@@ -204,8 +205,11 @@ private:
 namespace std {
 
 template<>
-TINS_API struct hash<Tins::IPv4Address> {
-    size_t operator()(const Tins::IPv4Address& addr) const;
+struct hash<Tins::IPv4Address> {
+    size_t operator()(const Tins::IPv4Address& addr) const
+    {
+        return std::hash<std::uint32_t>()(addr);
+    }
 };
 
 } // std
diff --git a/include/tins/ipv6_address.h b/include/tins/ipv6_address.h
index 454b9f7..aad0136 100644
--- a/include/tins/ipv6_address.h
+++ b/include/tins/ipv6_address.h
@@ -35,6 +35,7 @@
 #include <stdint.h>
 #include "cxxstd.h"
 #include "macros.h"
+#include <functional>
 
 namespace Tins {
 
@@ -222,8 +223,11 @@ private:
 namespace std {
 
 template<>
-TINS_API struct hash<Tins::IPv6Address> {
-    size_t operator()(const Tins::IPv6Address& addr) const;
+struct hash<Tins::IPv6Address> {
+    size_t operator()(const Tins::IPv6Address& addr) const
+    {
+        return std::hash<string>()(addr.to_string());
+    }
 };
 
 } // std
diff --git a/src/ip_address.cpp b/src/ip_address.cpp
index d6d1c95..cca9af4 100644
--- a/src/ip_address.cpp
+++ b/src/ip_address.cpp
@@ -154,13 +154,3 @@ IPv4Address IPv4Address::operator&(const IPv4Address& mask) const {
 }
 
 } // Tins
-
-#if TINS_IS_CXX11
-namespace std {
-
-size_t hash<Tins::IPv4Address>::operator()(const Tins::IPv4Address& addr) const {
-    return std::hash<uint32_t>()(addr);
-}
-
-} // std
-#endif // TINS_IS_CXX11
diff --git a/src/ipv6_address.cpp b/src/ipv6_address.cpp
index d9e5e3f..36e12c2 100644
--- a/src/ipv6_address.cpp
+++ b/src/ipv6_address.cpp
@@ -152,13 +152,3 @@ IPv6Address operator&(const IPv6Address& lhs, const IPv6Address& rhs) {
 }
 
 } // Tins
-
-#if TINS_IS_CXX11
-namespace std {
-
-size_t hash<Tins::IPv6Address>::operator()(const Tins::IPv6Address& addr) const {
-    return std::hash<string>()(addr.to_string());
-}
-
-} // std
-#endif // TINS_IS_CXX11