diff --git a/cxx/mcc_fsm.h b/cxx/mcc_fsm.h
index 0add90f..a11080f 100644
--- a/cxx/mcc_fsm.h
+++ b/cxx/mcc_fsm.h
@@ -17,14 +17,17 @@ namespace traits
 {
 
 template <typename T>
-concept fsm_event_c = std::is_default_constructible_v<T> && std::is_move_constructible_v<T> && std::movable<T>;
+concept fsm_event_c =
+    std::is_default_constructible_v<T> && std::is_move_constructible_v<T> && std::movable<T> && requires {
+        { T::ID } -> std::same_as<const std::string_view>;  // static constant member of event identificator
+    };
 
 template <typename T>
 concept fsm_state_c =
     std::is_default_constructible_v<T> && std::is_move_constructible_v<T> && std::movable<T> && requires {
         []<mcc::traits::pair_holder_c PHT>(std::type_identity<PHT>) {}(T::transition_t);
 
-        { T::name } -> std::same_as<const std::string_view>;  // static constant of state name
+        { T::ID } -> std::same_as<const std::string_view>;  // static constant member of state identificator
     };
 
 }  // namespace traits