diff --git a/libraries/chain/include/graphene/chain/son_object.hpp b/libraries/chain/include/graphene/chain/son_object.hpp
index 8ca126f7..0ec7a43b 100644
--- a/libraries/chain/include/graphene/chain/son_object.hpp
+++ b/libraries/chain/include/graphene/chain/son_object.hpp
@@ -78,6 +78,9 @@ namespace graphene { namespace chain {
          void pay_son_fee(share_type pay, database& db);
          bool has_valid_config()const;
          bool has_valid_config(time_point_sec head_block_time)const;
+
+         inline vote_id_type get_vote_id_bitcoin() const { return vote_id_bitcoin; }
+         inline vote_id_type get_vote_id_hive() const { return vote_id_hive; }
    };
 
    struct by_account;
@@ -93,10 +96,10 @@ namespace graphene { namespace chain {
             member<son_object, account_id_type, &son_object::son_account>
          >,
          ordered_unique< tag<by_vote_id_bitcoin>,
-            member<son_object, vote_id_type, &son_object::vote_id_bitcoin>
+            const_mem_fun<son_object, vote_id_type, &son_object::get_vote_id_bitcoin>
          >,
          ordered_unique< tag<by_vote_id_hive>,
-            member<son_object, vote_id_type, &son_object::vote_id_hive>
+            const_mem_fun<son_object, vote_id_type, &son_object::get_vote_id_hive>
          >
       >
    >;