diff --git a/src/cryptonote_core/master_node_list.cpp b/src/cryptonote_core/master_node_list.cpp
index b6e90a1c8fd..9bef9c2907a 100755
--- a/src/cryptonote_core/master_node_list.cpp
+++ b/src/cryptonote_core/master_node_list.cpp
@@ -876,6 +876,8 @@ namespace master_nodes
   master_node_info master_node_list::state_t::get_master_node_details(crypto::public_key mnode_key)
   {
     auto it = master_nodes_infos.find(mnode_key);
+    if (it == master_nodes_infos.end())
+      throw std::invalid_argument("get_master_node_details: master node not found");
     return *it->second;
   }
 
diff --git a/src/cryptonote_core/tx_pool.cpp b/src/cryptonote_core/tx_pool.cpp
index 28d4170a12f..b29b865b2e7 100755
--- a/src/cryptonote_core/tx_pool.cpp
+++ b/src/cryptonote_core/tx_pool.cpp
@@ -274,6 +274,8 @@ namespace cryptonote
           return false;
       
         uint64_t block_height = m_blockchain.get_current_blockchain_height();
+        if (!m_blockchain.get_master_node_list().is_master_node(mnode_key))
+          return false;
         const master_nodes::master_node_info &node_info = m_blockchain.get_master_node_list().get_master_node_details(mnode_key);
 
         for (const auto &contributor : node_info.contributors)