diff --git a/src/ip_address.cpp b/src/ip_address.cpp
index e2e892a..1d55c45 100644
--- a/src/ip_address.cpp
+++ b/src/ip_address.cpp
@@ -157,8 +157,11 @@ IPv4Address IPv4Address::operator&(const IPv4Address& mask) const {
 } // Tins
 
 #ifdef TINS_IS_CXX11
-// Hash
-size_t std::hash<Tins::IPv4Address>::operator()(const Tins::IPv4Address& addr) const {
+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 9a3ab79..6523cc5 100644
--- a/src/ipv6_address.cpp
+++ b/src/ipv6_address.cpp
@@ -154,8 +154,11 @@ IPv6Address operator&(const IPv6Address& lhs, const IPv6Address& rhs) {
 } // Tins
 
 #ifdef TINS_IS_CXX11
-// Hash
-size_t std::hash<Tins::IPv6Address>::operator()(const Tins::IPv6Address& addr) const {
+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