diff --git a/src/libutil/include/nix/util/util.hh b/src/libutil/include/nix/util/util.hh
index 2361bf2e7..37d14d4fb 100644
--- a/src/libutil/include/nix/util/util.hh
+++ b/src/libutil/include/nix/util/util.hh
@@ -223,18 +223,18 @@ std::pair<std::string_view, std::string_view> getLine(std::string_view s);
 /**
  * Get a value for the specified key from an associate container.
  */
-template <class T>
-const typename T::mapped_type * get(const T & map, const typename T::key_type & key)
+template <class T, typename K>
+const typename T::mapped_type * get(const T & map, K && key)
 {
-    auto i = map.find(key);
+    auto i = map.find(std::forward<K>(key));
     if (i == map.end()) return nullptr;
     return &i->second;
 }
 
-template <class T>
-typename T::mapped_type * get(T & map, const typename T::key_type & key)
+template <class T, typename K>
+typename T::mapped_type * get(T & map, K && key)
 {
-    auto i = map.find(key);
+    auto i = map.find(std::forward<K>(key));
     if (i == map.end()) return nullptr;
     return &i->second;
 }
@@ -242,12 +242,12 @@ typename T::mapped_type * get(T & map, const typename T::key_type & key)
 /**
  * Get a value for the specified key from an associate container, or a default value if the key isn't present.
  */
-template <class T>
+template <class T, typename K>
 const typename T::mapped_type & getOr(T & map,
-    const typename T::key_type & key,
+    K && key,
     const typename T::mapped_type & defaultValue)
 {
-    auto i = map.find(key);
+    auto i = map.find(std::forward<K>(key));
     if (i == map.end()) return defaultValue;
     return i->second;
 }