diff --git a/include/game_interface.h b/include/game_interface.h
index 931e717..281f130 100644
--- a/include/game_interface.h
+++ b/include/game_interface.h
@@ -4,7 +4,6 @@
 #include <cstddef>
 #include <iosfwd>
 #include <vector>
-#include <unordered_map>
 #include <memory>
 
 #include "hanabi_types.hpp"
@@ -71,7 +70,7 @@ namespace Hanabi
 
     [[nodiscard]] virtual std::uint64_t enumerated_states() const = 0;
 
-    [[nodiscard]] virtual const std::unordered_map<unsigned long, probability_t> & position_tablebase() const = 0;
+    [[nodiscard]] virtual const map_type<unsigned long, probability_t> & position_tablebase() const = 0;
 
     virtual void init_backtracking_information() = 0;
 
diff --git a/include/game_state.h b/include/game_state.h
index 8e6cc97..6fcf0c7 100644
--- a/include/game_state.h
+++ b/include/game_state.h
@@ -9,7 +9,6 @@
 #include <optional>
 #include <ostream>
 #include <stack>
-#include <unordered_map>
 #include <vector>
 #include <memory>
 
@@ -117,7 +116,7 @@ namespace Hanabi
 
     [[nodiscard]] std::uint64_t enumerated_states() const final;
 
-    [[nodiscard]] const std::unordered_map<unsigned long, probability_t> & position_tablebase() const final;
+    [[nodiscard]] const map_type<unsigned long, probability_t> & position_tablebase() const final;
 
     void init_backtracking_information() final;
 
@@ -258,7 +257,7 @@ namespace Hanabi
     RelativeRepresentationData _relative_representation;
 
     // Lookup table for states. Uses the ids calculated using the relative representation
-    std::unordered_map<unsigned long, probability_t> _position_tablebase;
+    map_type<unsigned long, probability_t> _position_tablebase;
 
     std::uint64_t _enumerated_states{};
   };
diff --git a/include/game_state.hpp b/include/game_state.hpp
index 75b5e3b..06a992e 100644
--- a/include/game_state.hpp
+++ b/include/game_state.hpp
@@ -1336,7 +1336,7 @@ namespace Hanabi
   }
 
   template<suit_t num_suits, player_t num_players, hand_index_t hand_size>
-  const std::unordered_map<unsigned long, probability_t> &
+  const map_type<unsigned long, probability_t> &
   HanabiState<num_suits, num_players, hand_size>::position_tablebase() const
   {
     return _position_tablebase;
diff --git a/include/hanabi_types.hpp b/include/hanabi_types.hpp
index 93980b8..730e6d3 100644
--- a/include/hanabi_types.hpp
+++ b/include/hanabi_types.hpp
@@ -8,6 +8,8 @@
 
 #include <boost/rational.hpp>
 
+#include <unordered_map>
+
 namespace Hanabi
 {
 
@@ -20,6 +22,9 @@ namespace Hanabi
   using probability_base_type = unsigned long;
   using rational_probability = boost::rational<probability_base_type>;
 
+  template<class Key, class Value>
+  using map_type = std::unordered_map<Key, Value>;
+
 /**
  * Define macro
  * NUSE_RATIONAL_PROBABILITIES