diff --git a/rai/common.hpp b/rai/common.hpp
index de6d9b9a..b8e545a8 100644
--- a/rai/common.hpp
+++ b/rai/common.hpp
@@ -221,6 +221,7 @@ enum class process_result
 	unreceivable, // Source block doesn't exist or has already been received
 	gap_previous, // Block marked as previous is unknown
 	gap_source, // Block marked as source is unknown
+	utx_disabled, // Awaiting UTX canary block
 	not_receive_from_send, // Receive does not have a send source
 	account_mismatch, // Account number in open block doesn't match send destination
 	opened_burn_account, // The impossible happened, someone found the private key associated with the public key '0'.
diff --git a/rai/core_test/ledger.cpp b/rai/core_test/ledger.cpp
index e76f579c..83f5aeab 100644
--- a/rai/core_test/ledger.cpp
+++ b/rai/core_test/ledger.cpp
@@ -1478,6 +1478,7 @@ TEST (ledger, block_destination_source)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair dest;
@@ -1522,6 +1523,7 @@ TEST (ledger, utx_account)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1536,6 +1538,7 @@ TEST (ledger, utx_send_receive)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1567,6 +1570,7 @@ TEST (ledger, utx_receive)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::send_block send1 (genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1596,6 +1600,7 @@ TEST (ledger, utx_rep_change)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair rep;
@@ -1618,6 +1623,7 @@ TEST (ledger, utx_open)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1651,6 +1657,7 @@ TEST (ledger, send_after_utx_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1667,6 +1674,7 @@ TEST (ledger, receive_after_utx_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1683,6 +1691,7 @@ TEST (ledger, change_after_utx_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1699,6 +1708,7 @@ TEST (ledger, utx_unreceivable_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::send_block send1 (genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1721,6 +1731,7 @@ TEST (ledger, utx_receive_bad_amount_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::send_block send1 (genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1743,6 +1754,7 @@ TEST (ledger, utx_no_link_amount_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1759,6 +1771,7 @@ TEST (ledger, utx_receive_wrong_account_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1782,6 +1795,7 @@ TEST (ledger, utx_open_utx_fork)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1801,6 +1815,7 @@ TEST (ledger, utx_utx_open_fork)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1820,6 +1835,7 @@ TEST (ledger, utx_open_previous_fail)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1836,6 +1852,7 @@ TEST (ledger, utx_send_change)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair rep;
@@ -1858,6 +1875,7 @@ TEST (ledger, utx_receive_change)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1889,6 +1907,7 @@ TEST (ledger, utx_open_old)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1908,6 +1927,7 @@ TEST (ledger, utx_receive_old)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -1931,6 +1951,7 @@ TEST (ledger, utx_rollback_send)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1960,6 +1981,7 @@ TEST (ledger, utx_rollback_receive)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -1984,6 +2006,7 @@ TEST (ledger, utx_rollback_received_send)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair key;
@@ -2009,6 +2032,7 @@ TEST (ledger, utx_rep_change_rollback)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair rep;
@@ -2028,6 +2052,7 @@ TEST (ledger, utx_open_rollback)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair destination;
@@ -2052,6 +2077,7 @@ TEST (ledger, utx_send_change_rollback)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::keypair rep;
@@ -2071,6 +2097,7 @@ TEST (ledger, utx_receive_change_rollback)
 	ASSERT_TRUE (!init);
 	rai::ledger ledger (store);
 	rai::genesis genesis;
+	ledger.utx_parse_canary = genesis.hash ();
 	rai::transaction transaction (store.environment, nullptr, true);
 	genesis.initialize (transaction, store);
 	rai::utx_block send1 (rai::genesis_account, genesis.hash (), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -2084,3 +2111,26 @@ TEST (ledger, utx_receive_change_rollback)
 	ASSERT_EQ (rai::genesis_amount - rai::Gxrb_ratio, ledger.weight (transaction, rai::genesis_account));
 	ASSERT_EQ (0, ledger.weight (transaction, rep.pub));
 }
+
+TEST (ledger, utx_canary_blocks)
+{
+	bool init (false);
+	rai::block_store store (init, rai::unique_path ());
+	ASSERT_TRUE (!init);
+	rai::genesis genesis;
+	rai::send_block parse_canary (genesis.hash (), rai::test_genesis_key.pub, rai::genesis_amount, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
+	rai::send_block generate_canary (parse_canary.hash (), rai::test_genesis_key.pub, rai::genesis_amount, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
+	rai::ledger ledger (store, 0, parse_canary.hash (), generate_canary.hash ());
+	rai::transaction transaction (store.environment, nullptr, true);
+	genesis.initialize (transaction, store);
+	rai::utx_block utx (rai::test_genesis_key.pub, genesis.hash (), rai::test_genesis_key.pub, rai::genesis_amount - rai::Gxrb_ratio, rai::test_genesis_key.pub, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
+	ASSERT_FALSE (ledger.utx_parsing_enabled (transaction));
+	ASSERT_FALSE (ledger.utx_generation_enabled (transaction));
+	ASSERT_EQ (rai::process_result::utx_disabled, ledger.process (transaction, utx).code);
+	ASSERT_EQ (rai::process_result::progress, ledger.process (transaction, parse_canary).code);
+	ASSERT_TRUE (ledger.utx_parsing_enabled (transaction));
+	ASSERT_FALSE (ledger.utx_generation_enabled (transaction));
+	ASSERT_EQ (rai::process_result::progress, ledger.process (transaction, generate_canary).code);
+	ASSERT_TRUE (ledger.utx_parsing_enabled (transaction));
+	ASSERT_TRUE (ledger.utx_generation_enabled (transaction));
+}
diff --git a/rai/core_test/network.cpp b/rai/core_test/network.cpp
index dcab2e67..480e902c 100644
--- a/rai/core_test/network.cpp
+++ b/rai/core_test/network.cpp
@@ -554,8 +554,10 @@ TEST (bootstrap_processor, process_two)
 TEST (bootstrap_processor, process_utx)
 {
 	rai::system system (24000, 1);
+	rai::genesis genesis;
 	system.wallet (0)->insert_adhoc (rai::test_genesis_key.prv);
 	auto node0 (system.nodes[0]);
+	node0->ledger.utx_parse_canary = genesis.hash ();
 	std::unique_ptr<rai::block> block1 (new rai::utx_block (rai::test_genesis_key.pub, node0->latest (rai::test_genesis_key.pub), rai::test_genesis_key.pub, rai::genesis_amount - 100, rai::test_genesis_key.pub, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0));
 	std::unique_ptr<rai::block> block2 (new rai::utx_block (rai::test_genesis_key.pub, block1->hash (), rai::test_genesis_key.pub, rai::genesis_amount, block1->hash (), rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0));
 	node0->generate_work (*block1);
@@ -564,6 +566,7 @@ TEST (bootstrap_processor, process_utx)
 	node0->process (*block2);
 	rai::node_init init1;
 	auto node1 (std::make_shared<rai::node> (init1, system.service, 24001, rai::unique_path (), system.alarm, system.logging, system.work));
+	node1->ledger.utx_parse_canary = genesis.hash ();
 	ASSERT_EQ (node0->latest (rai::test_genesis_key.pub), block2->hash ());
 	ASSERT_NE (node1->latest (rai::test_genesis_key.pub), block2->hash ());
 	node1->bootstrap_initiator.bootstrap (node0->network.endpoint ());
diff --git a/rai/core_test/rpc.cpp b/rai/core_test/rpc.cpp
index 584fef99..537e772b 100644
--- a/rai/core_test/rpc.cpp
+++ b/rai/core_test/rpc.cpp
@@ -880,6 +880,8 @@ TEST (rpc, history)
 	auto receive (system.wallet (0)->receive_action (static_cast<rai::send_block &> (*send), rai::test_genesis_key.pub, system.nodes[0]->config.receive_minimum.number ()));
 	ASSERT_NE (nullptr, receive);
 	auto node0 (system.nodes[0]);
+	rai::genesis genesis;
+	node0->ledger.utx_parse_canary = genesis.hash ();
 	rai::utx_block usend (rai::genesis_account, node0->latest (rai::genesis_account), rai::genesis_account, rai::genesis_amount - rai::Gxrb_ratio, rai::genesis_account, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
 	rai::utx_block ureceive (rai::genesis_account, usend.hash (), rai::genesis_account, rai::genesis_amount, usend.hash (), rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
 	rai::utx_block uchange (rai::genesis_account, ureceive.hash (), rai::keypair ().pub, rai::genesis_amount, 0, rai::test_genesis_key.prv, rai::test_genesis_key.pub, 0);
@@ -925,7 +927,6 @@ TEST (rpc, history)
 	ASSERT_EQ (rai::test_genesis_key.pub.to_account (), std::get<1> (history_l[3]));
 	ASSERT_EQ (system.nodes[0]->config.receive_minimum.to_string_dec (), std::get<2> (history_l[3]));
 	ASSERT_EQ (send->hash ().to_string (), std::get<3> (history_l[3]));
-	rai::genesis genesis;
 	ASSERT_EQ ("receive", std::get<0> (history_l[4]));
 	ASSERT_EQ (rai::test_genesis_key.pub.to_account (), std::get<1> (history_l[4]));
 	ASSERT_EQ (rai::genesis_amount.convert_to<std::string> (), std::get<2> (history_l[4]));
@@ -3172,6 +3173,7 @@ TEST (rpc, block_create_utx)
 	rai::system system (24000, 1);
 	rai::keypair key;
 	rai::genesis genesis;
+	system.nodes[0]->ledger.utx_parse_canary = genesis.hash ();
 	system.wallet (0)->insert_adhoc (rai::test_genesis_key.prv);
 	boost::property_tree::ptree request;
 	request.put ("action", "block_create");
diff --git a/rai/ledger.cpp b/rai/ledger.cpp
index fe34a077..fb31f140 100644
--- a/rai/ledger.cpp
+++ b/rai/ledger.cpp
@@ -167,12 +167,22 @@ public:
 	void open_block (rai::open_block const &) override;
 	void change_block (rai::change_block const &) override;
 	void utx_block (rai::utx_block const &) override;
+	void utx_block_impl (rai::utx_block const &);
 	rai::ledger & ledger;
 	MDB_txn * transaction;
 	rai::process_return result;
 };
 
 void ledger_processor::utx_block (rai::utx_block const & block_a)
+{
+	result.code = ledger.utx_parsing_enabled (transaction) ? rai::process_result::progress : rai::process_result::utx_disabled;
+	if (result.code == rai::process_result::progress)
+	{
+		utx_block_impl (block_a);
+	}
+}
+
+void ledger_processor::utx_block_impl (rai::utx_block const & block_a)
 {
 	auto hash (block_a.hash ());
 	auto existing (ledger.store.block_exists (transaction, hash));
@@ -481,10 +491,12 @@ bool rai::shared_ptr_block_hash::operator() (std::shared_ptr<rai::block> const &
 	return *lhs == *rhs;
 }
 
-rai::ledger::ledger (rai::block_store & store_a, rai::uint128_t const & inactive_supply_a) :
+rai::ledger::ledger (rai::block_store & store_a, rai::uint128_t const & inactive_supply_a, rai::block_hash const & utx_parse_canary_a, rai::block_hash const & utx_generate_canary_a) :
 store (store_a),
 inactive_supply (inactive_supply_a),
-check_bootstrap_weights (true)
+check_bootstrap_weights (true),
+utx_parse_canary (utx_parse_canary_a),
+utx_generate_canary (utx_generate_canary_a)
 {
 }
 
@@ -778,9 +790,14 @@ void rai::ledger::dump_account_chain (rai::account const & account_a)
 	}
 }
 
-bool rai::ledger::utx_enabled (MDB_txn * transaction_a)
+bool rai::ledger::utx_parsing_enabled (MDB_txn * transaction_a)
 {
-	return false;
+	return store.block_exists (transaction_a, utx_parse_canary);
+}
+
+bool rai::ledger::utx_generation_enabled (MDB_txn * transaction_a)
+{
+	return utx_parsing_enabled (transaction_a) && store.block_exists (transaction_a, utx_generate_canary);
 }
 
 void rai::ledger::checksum_update (MDB_txn * transaction_a, rai::block_hash const & hash_a)
diff --git a/rai/ledger.hpp b/rai/ledger.hpp
index c345e29d..3cd17fec 100644
--- a/rai/ledger.hpp
+++ b/rai/ledger.hpp
@@ -16,7 +16,7 @@ public:
 class ledger
 {
 public:
-	ledger (rai::block_store &, rai::uint128_t const & = 0);
+	ledger (rai::block_store &, rai::uint128_t const & = 0, rai::block_hash const & = 0, rai::block_hash const & = 0);
 	std::pair<rai::uint128_t, std::shared_ptr<rai::block>> winner (MDB_txn *, rai::votes const & votes_a);
 	// Map of weight -> associated block, ordered greatest to least
 	std::map<rai::uint128_t, std::shared_ptr<rai::block>, std::greater<rai::uint128_t>> tally (MDB_txn *, rai::votes const &);
@@ -45,12 +45,15 @@ public:
 	void checksum_update (MDB_txn *, rai::block_hash const &);
 	rai::checksum checksum (MDB_txn *, rai::account const &, rai::account const &);
 	void dump_account_chain (rai::account const &);
-	bool utx_enabled (MDB_txn *);
+	bool utx_parsing_enabled (MDB_txn *);
+	bool utx_generation_enabled (MDB_txn *);
 	static rai::uint128_t const unit;
 	rai::block_store & store;
 	rai::uint128_t inactive_supply;
 	std::unordered_map<rai::account, rai::uint128_t> bootstrap_weights;
 	uint64_t bootstrap_weight_max_blocks;
 	std::atomic<bool> check_bootstrap_weights;
+	rai::block_hash utx_parse_canary;
+	rai::block_hash utx_generate_canary;
 };
 };
diff --git a/rai/node/node.cpp b/rai/node/node.cpp
index 8007259a..add91a1d 100644
--- a/rai/node/node.cpp
+++ b/rai/node/node.cpp
@@ -1295,6 +1295,16 @@ rai::process_return rai::block_processor::process_receive_one (MDB_txn * transac
 			node.gap_cache.add (transaction_a, block_a);
 			break;
 		}
+		case rai::process_result::utx_disabled:
+		{
+			if (node.config.logging.ledger_logging ())
+			{
+				BOOST_LOG (node.log) << boost::str (boost::format ("UTX blocks are disabled: %1%") % block_a->hash ().to_string ());
+			}
+			node.store.unchecked_put (transaction_a, node.ledger.utx_parse_canary, block_a);
+			node.gap_cache.add (transaction_a, block_a);
+			break;
+		}
 		case rai::process_result::old:
 		{
 			{
diff --git a/rai/node/rpc.cpp b/rai/node/rpc.cpp
index d16c252b..6059cf3c 100644
--- a/rai/node/rpc.cpp
+++ b/rai/node/rpc.cpp
@@ -2507,6 +2507,11 @@ void rai::rpc_handler::process ()
 					error_response (response, "Gap source block");
 					break;
 				}
+				case rai::process_result::utx_disabled:
+				{
+					error_response (response, "UTX blocks are disabled");
+					break;
+				}
 				case rai::process_result::old:
 				{
 					error_response (response, "Old block");
diff --git a/rai/node/testing.cpp b/rai/node/testing.cpp
index ff3f0021..9703fd5f 100644
--- a/rai/node/testing.cpp
+++ b/rai/node/testing.cpp
@@ -303,7 +303,7 @@ void rai::system::generate_mass_activity (uint32_t count_a, rai::node & node_a)
 				count = block_counts.sum ();
 				utx = block_counts.utx;
 			}
-			std::cerr << boost::str (boost::format ("Mass activity iteration %1% us %2% us/t %3% utx: %4% count: %5%\n") % i % us % (us / 256) % utx % count);
+			std::cerr << boost::str (boost::format ("Mass activity iteration %1% us %2% us/t %3% utx: %4% old: %5%\n") % i % us % (us / 256) % utx % (count - utx));
 			previous = now;
 		}
 		generate_activity (node_a, accounts);
diff --git a/rai/node/wallet.cpp b/rai/node/wallet.cpp
index d0297d1e..04d62957 100644
--- a/rai/node/wallet.cpp
+++ b/rai/node/wallet.cpp
@@ -865,7 +865,7 @@ std::shared_ptr<rai::block> rai::wallet::receive_action (rai::block const & send
 					{
 						std::shared_ptr<rai::block> rep_block = node.ledger.store.block_get (transaction, info.rep_block);
 						assert (rep_block != nullptr);
-						if (node.ledger.utx_enabled (transaction))
+						if (node.ledger.utx_generation_enabled (transaction))
 						{
 							block.reset (new rai::utx_block (account, info.head, rep_block->representative (), info.balance.number () + pending_info.amount.number (), hash, prv, account, generate_work_a ? work_fetch (transaction, account, info.head) : 0));
 						}
@@ -876,7 +876,7 @@ std::shared_ptr<rai::block> rai::wallet::receive_action (rai::block const & send
 					}
 					else
 					{
-						if (node.ledger.utx_enabled (transaction))
+						if (node.ledger.utx_generation_enabled (transaction))
 						{
 							block.reset (new rai::utx_block (account, info.head, representative_a, pending_info.amount, hash, prv, account, generate_work_a ? work_fetch (transaction, account, account) : 0));
 						}
@@ -940,7 +940,7 @@ std::shared_ptr<rai::block> rai::wallet::change_action (rai::account const & sou
 				rai::raw_key prv;
 				auto error2 (store.fetch (transaction, source_a, prv));
 				assert (!error2);
-				if (node.ledger.utx_enabled (transaction))
+				if (node.ledger.utx_generation_enabled (transaction))
 				{
 					block.reset (new rai::utx_block (source_a, info.head, representative_a, info.balance, 0, prv, source_a, generate_work_a ? work_fetch (transaction, source_a, info.head) : 0));
 				}
@@ -1017,7 +1017,7 @@ std::shared_ptr<rai::block> rai::wallet::send_action (rai::account const & sourc
 						assert (!error2);
 						std::shared_ptr<rai::block> rep_block = node.ledger.store.block_get (transaction, info.rep_block);
 						assert (rep_block != nullptr);
-						if (node.ledger.utx_enabled (transaction))
+						if (node.ledger.utx_generation_enabled (transaction))
 						{
 							block.reset (new rai::utx_block (source_a, info.head, rep_block->representative (), balance - amount_a, account_a, prv, source_a, generate_work_a ? work_fetch (transaction, source_a, info.head) : 0));
 						}
diff --git a/rai/qt/qt.cpp b/rai/qt/qt.cpp
index 16cf212d..15fc8ea9 100644
--- a/rai/qt/qt.cpp
+++ b/rai/qt/qt.cpp
@@ -1103,7 +1103,7 @@ void rai_qt::wallet::start ()
 		if (auto this_l = this_w.lock ())
 		{
 			auto account (result_a.account);
-			this_l->application.postEvent (&this_l->processor, new eventloop_event ([ this_w, block_a, account ]() {
+			this_l->application.postEvent (&this_l->processor, new eventloop_event ([this_w, block_a, account]() {
 				if (auto this_l = this_w.lock ())
 				{
 					if (this_l->wallet_m->exists (account))
diff --git a/rai/slow_test/node.cpp b/rai/slow_test/node.cpp
index efd29cad..8b441405 100644
--- a/rai/slow_test/node.cpp
+++ b/rai/slow_test/node.cpp
@@ -34,6 +34,39 @@ TEST (system, generate_mass_activity_long)
 	runner.join ();
 }
 
+TEST (system, generate_mass_activity_utx_enable)
+{
+	rai::system system (24000, 1);
+	rai::thread_runner runner (system.service, system.nodes[0]->config.io_threads);
+	system.wallet (0)->insert_adhoc (rai::test_genesis_key.prv);
+	system.nodes[0]->alarm.add (std::chrono::steady_clock::now () + std::chrono::minutes (1), [&system]() {
+		std::cerr << boost::str (boost::format ("Enabling utx block parsing\n"));
+		rai::transaction transaction (system.nodes[0]->store.environment, nullptr, true);
+		ASSERT_FALSE (system.nodes[0]->ledger.utx_parsing_enabled (transaction));
+		rai::genesis genesis;
+		system.nodes[0]->ledger.utx_parse_canary = genesis.hash ();
+		ASSERT_TRUE (system.nodes[0]->ledger.utx_parsing_enabled (transaction));
+	});
+	system.nodes[0]->alarm.add (std::chrono::steady_clock::now () + std::chrono::minutes (2), [&system]() {
+		std::cerr << boost::str (boost::format ("Enabling utx block generation\n"));
+		rai::transaction transaction (system.nodes[0]->store.environment, nullptr, true);
+		ASSERT_FALSE (system.nodes[0]->ledger.utx_generation_enabled (transaction));
+		rai::genesis genesis;
+		system.nodes[0]->ledger.utx_generate_canary = genesis.hash ();
+		ASSERT_TRUE (system.nodes[0]->ledger.utx_generation_enabled (transaction));
+	});
+	size_t count (1000000000);
+	system.generate_mass_activity (count, *system.nodes[0]);
+	size_t accounts (0);
+	rai::transaction transaction (system.nodes[0]->store.environment, nullptr, false);
+	for (auto i (system.nodes[0]->store.latest_begin (transaction)), n (system.nodes[0]->store.latest_end ()); i != n; ++i)
+	{
+		++accounts;
+	}
+	system.stop ();
+	runner.join ();
+}
+
 TEST (system, receive_while_synchronizing)
 {
 	std::vector<std::thread> threads;