diff --git a/src/Memory/BorrowedPtr.hpp b/src/Memory/BorrowedPtr.hpp
index b7a2d7d..438c711 100644
--- a/src/Memory/BorrowedPtr.hpp
+++ b/src/Memory/BorrowedPtr.hpp
@@ -52,4 +52,12 @@ namespace ArbUt {
     };
 }
 
+namespace std {
+
+    template <class T> struct hash<ArbUt::BorrowedPtr<T>> {
+        std::size_t operator()(const ArbUt::BorrowedPtr<T>& k) const { return (size_t)k.GetRaw(); }
+    };
+
+}
+
 #endif // ARBUTILS_BORROWEDPTR_HPP