diff --git a/libs/util/include/psemek/util/hash_table.hpp b/libs/util/include/psemek/util/hash_table.hpp
index 2de28b0e..1c975352 100644
--- a/libs/util/include/psemek/util/hash_table.hpp
+++ b/libs/util/include/psemek/util/hash_table.hpp
@@ -373,17 +373,14 @@ namespace psemek::util
 				: Hash(hash)
 			{}
 
-			std::size_t operator()(Key const & key) const
+			template <typename Key1>
+			std::size_t operator()(Key1 const & key) const
 			{
 				return static_cast<Hash const &>(*this)(key);
 			}
 
-			std::size_t operator()(std::pair<Key const, Value> const & pair) const
-			{
-				return static_cast<Hash const &>(*this)(pair.first);
-			}
-
-			std::size_t operator()(std::pair<Key, Value> const & pair) const
+			template <typename Key1, typename Value1>
+			std::size_t operator()(std::pair<Key1, Value1> const & pair) const
 			{
 				return static_cast<Hash const &>(*this)(pair.first);
 			}
@@ -397,22 +394,20 @@ namespace psemek::util
 				: Equal(equal)
 			{}
 
-			bool operator()(Key const & key1, std::pair<Key const, Value> const & pair2) const
+			template <typename Key1, typename Key2, typename Value2>
+			bool operator()(Key1 const & key1, std::pair<Key2, Value2> const & pair2) const
 			{
 				return static_cast<Equal const &>(*this)(key1, pair2.first);
 			}
 
-			bool operator()(std::pair<Key const, Value> const & pair1, Key const & key2) const
+			template <typename Key1, typename Value1, typename Key2>
+			bool operator()(std::pair<Key1, Value1> const & pair1, Key2 const & key2) const
 			{
 				return static_cast<Equal const &>(*this)(pair1.first, key2);
 			}
 
-			bool operator()(std::pair<Key const, Value> const & pair1, std::pair<Key const, Value> const & pair2) const
-			{
-				return static_cast<Equal const &>(*this)(pair1.first, pair2.first);
-			}
-
-			bool operator()(std::pair<Key, Value> const & pair1, std::pair<Key const, Value> const & pair2) const
+			template <typename Key1, typename Value1, typename Key2, typename Value2>
+			bool operator()(std::pair<Key1, Value1> const & pair1, std::pair<Key2, Value2> const & pair2) const
 			{
 				return static_cast<Equal const &>(*this)(pair1.first, pair2.first);
 			}
@@ -644,7 +639,7 @@ namespace psemek::util
 		{
 			auto it = find(key);
 			if (it == end())
-				throw util::key_error{key};
+				throw util::key_error<Key>(key);
 			return it->second;
 		}
 
@@ -653,7 +648,7 @@ namespace psemek::util
 		{
 			auto it = find(key);
 			if (it == end())
-				throw util::key_error{key};
+				throw util::key_error<Key>(key);
 			return it->second;
 		}
 
@@ -661,7 +656,7 @@ namespace psemek::util
 		{
 			auto it = find(key);
 			if (it == end())
-				throw util::key_error{key};
+				throw util::key_error<Key>(key);
 			return it->second;
 		}
 
@@ -670,7 +665,7 @@ namespace psemek::util
 		{
 			auto it = find(key);
 			if (it == end())
-				throw util::key_error{key};
+				throw util::key_error<Key>(key);
 			return it->second;
 		}