diff --git a/src/block_template.cpp b/src/block_template.cpp
index ae90db2..d35cdcd 100644
--- a/src/block_template.cpp
+++ b/src/block_template.cpp
@@ -266,7 +266,22 @@ void BlockTemplate::update(const MinerData& data, const Mempool& mempool, Wallet
 
 	m_blockHeaderSize = m_blockHeader.size();
 
-	get_tx_keys(m_poolBlockTemplate->m_txkeyPub, m_poolBlockTemplate->m_txkeySec, miner_wallet->spend_public_key(), data.prev_id);
+	const int sidechain_version = m_poolBlockTemplate->get_sidechain_version();
+
+	if (sidechain_version > 1) {
+		static_assert(decltype(m_rng)::word_size == 64, "m_rng must be 64-bit");
+
+		uint64_t* p = reinterpret_cast<uint64_t*>(m_poolBlockTemplate->m_txkeySecSeed.h);
+		for (size_t i = 0; i < HASH_SIZE / sizeof(uint64_t); ++i) {
+			p[i] = m_rng();
+		}
+
+		get_tx_keys(m_poolBlockTemplate->m_txkeyPub, m_poolBlockTemplate->m_txkeySec, m_poolBlockTemplate->m_txkeySecSeed, data.prev_id);
+	}
+	else {
+		get_tx_keys(m_poolBlockTemplate->m_txkeyPub, m_poolBlockTemplate->m_txkeySec, miner_wallet->spend_public_key(), data.prev_id);
+	}
+
 	m_poolBlockTemplate->m_minerWallet = *miner_wallet;
 
 	m_sidechain->fill_sidechain_data(*m_poolBlockTemplate, m_shares);
@@ -602,7 +617,7 @@ void BlockTemplate::update(const MinerData& data, const Mempool& mempool, Wallet
 	{
 		memset(m_sidechainHashKeccakState, 0, sizeof(m_sidechainHashKeccakState));
 
-		const size_t extra_nonce_offset = m_sidechainHashBlob.size() - HASH_SIZE - ((m_poolBlockTemplate->get_sidechain_version() > 1) ? EXTRA_NONCE_SIZE : 0);
+		const size_t extra_nonce_offset = m_sidechainHashBlob.size() - HASH_SIZE - ((sidechain_version > 1) ? EXTRA_NONCE_SIZE : 0);
 		if (extra_nonce_offset >= KeccakParams::HASH_DATA_AREA) {
 			// Sidechain data is big enough to cache keccak state up to extra_nonce
 			m_sidechainHashInputLength = (extra_nonce_offset / KeccakParams::HASH_DATA_AREA) * KeccakParams::HASH_DATA_AREA;
diff --git a/src/crypto.cpp b/src/crypto.cpp
index d7be7f2..e253b24 100644
--- a/src/crypto.cpp
+++ b/src/crypto.cpp
@@ -266,10 +266,10 @@ public:
 		return true;
 	}
 
-	void get_tx_keys(hash& pub, hash& sec, const hash& wallet_spend_key, const hash& monero_block_id)
+	void get_tx_keys(hash& pub, hash& sec, const hash& seed, const hash& monero_block_id)
 	{
 		std::array<uint8_t, HASH_SIZE * 2> index;
-		memcpy(index.data(), wallet_spend_key.h, HASH_SIZE);
+		memcpy(index.data(), seed.h, HASH_SIZE);
 		memcpy(index.data() + HASH_SIZE, monero_block_id.h, HASH_SIZE);
 
 		{
@@ -287,7 +287,7 @@ public:
 		uint8_t entropy[N + HASH_SIZE * 2];
 
 		memcpy(entropy, domain, N);
-		memcpy(entropy + N, wallet_spend_key.h, HASH_SIZE);
+		memcpy(entropy + N, seed.h, HASH_SIZE);
 		memcpy(entropy + N + HASH_SIZE, monero_block_id.h, HASH_SIZE);
 
 		generate_keys_deterministic(pub, sec, entropy, sizeof(entropy));
@@ -399,9 +399,9 @@ bool derive_public_key(const hash& derivation, size_t output_index, const hash&
 	return cache->get_public_key(derivation, output_index, base, derived_key);
 }
 
-void get_tx_keys(hash& pub, hash& sec, const hash& wallet_spend_key, const hash& monero_block_id)
+void get_tx_keys(hash& pub, hash& sec, const hash& seed, const hash& monero_block_id)
 {
-	cache->get_tx_keys(pub, sec, wallet_spend_key, monero_block_id);
+	cache->get_tx_keys(pub, sec, seed, monero_block_id);
 }
 
 void derive_view_tag(const hash& derivation, size_t output_index, uint8_t& view_tag)
diff --git a/src/crypto.h b/src/crypto.h
index 2ab908c..ab5c6cd 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -21,7 +21,7 @@ namespace p2pool {
 
 void generate_keys(hash& pub, hash& sec);
 void generate_keys_deterministic(hash& pub, hash& sec, const uint8_t* entropy, size_t len);
-void get_tx_keys(hash& pub, hash& sec, const hash& wallet_spend_key, const hash& monero_block_id);
+void get_tx_keys(hash& pub, hash& sec, const hash& seed, const hash& monero_block_id);
 bool check_keys(const hash& pub, const hash& sec);
 bool generate_key_derivation(const hash& key1, const hash& key2, size_t output_index, hash& derivation, uint8_t& view_tag);
 bool derive_public_key(const hash& derivation, size_t output_index, const hash& base, hash& derived_key);
diff --git a/src/pool_block.cpp b/src/pool_block.cpp
index 92fe2f4..07bc35e 100644
--- a/src/pool_block.cpp
+++ b/src/pool_block.cpp
@@ -38,6 +38,7 @@ PoolBlock::PoolBlock()
 	, m_txkeyPub{}
 	, m_extraNonceSize(0)
 	, m_extraNonce(0)
+	, m_txkeySecSeed{}
 	, m_txkeySec{}
 	, m_parent{}
 	, m_sidechainHeight(0)
@@ -91,6 +92,7 @@ PoolBlock& PoolBlock::operator=(const PoolBlock& b)
 	m_extraNonce = b.m_extraNonce;
 	m_transactions = b.m_transactions;
 	m_minerWallet = b.m_minerWallet;
+	m_txkeySecSeed = b.m_txkeySecSeed;
 	m_txkeySec = b.m_txkeySec;
 	m_parent = b.m_parent;
 	m_uncles = b.m_uncles;
@@ -235,9 +237,18 @@ std::vector<uint8_t> PoolBlock::serialize_sidechain_data() const
 	const hash& spend = m_minerWallet.spend_public_key();
 	const hash& view = m_minerWallet.view_public_key();
 
+	const int sidechain_version = get_sidechain_version();
+
 	data.insert(data.end(), spend.h, spend.h + HASH_SIZE);
 	data.insert(data.end(), view.h, view.h + HASH_SIZE);
-	data.insert(data.end(), m_txkeySec.h, m_txkeySec.h + HASH_SIZE);
+
+	if (sidechain_version > 1) {
+		data.insert(data.end(), m_txkeySecSeed.h, m_txkeySecSeed.h + HASH_SIZE);
+	}
+	else {
+		data.insert(data.end(), m_txkeySec.h, m_txkeySec.h + HASH_SIZE);
+	}
+
 	data.insert(data.end(), m_parent.h, m_parent.h + HASH_SIZE);
 
 	writeVarint(m_uncles.size(), data);
@@ -254,7 +265,7 @@ std::vector<uint8_t> PoolBlock::serialize_sidechain_data() const
 	writeVarint(m_cumulativeDifficulty.lo, data);
 	writeVarint(m_cumulativeDifficulty.hi, data);
 
-	if (get_sidechain_version() > 1) {
+	if (sidechain_version > 1) {
 		const uint8_t* p = reinterpret_cast<const uint8_t*>(m_sidechainExtraBuf);
 		data.insert(data.end(), p, p + sizeof(m_sidechainExtraBuf));
 	}
diff --git a/src/pool_block.h b/src/pool_block.h
index f444713..2e2bc4a 100644
--- a/src/pool_block.h
+++ b/src/pool_block.h
@@ -106,6 +106,7 @@ struct PoolBlock
 
 	// Transaction secret key
 	// Required to check that pub keys in the miner transaction pay out to correct miner wallet addresses
+	hash m_txkeySecSeed;
 	hash m_txkeySec;
 
 	// Side-chain parent and uncle blocks
diff --git a/src/pool_block_parser.inl b/src/pool_block_parser.inl
index f7cb2c9..79a5c34 100644
--- a/src/pool_block_parser.inl
+++ b/src/pool_block_parser.inl
@@ -260,20 +260,33 @@ int PoolBlock::deserialize(const uint8_t* data, size_t size, const SideChain& si
 			return __LINE__;
 		}
 
-		READ_BUF(m_txkeySec.h, HASH_SIZE);
+		READ_BUF(m_txkeySecSeed.h, HASH_SIZE);
 
-		if (!check_keys(m_txkeyPub, m_txkeySec)) {
-			return __LINE__;
-		}
+		const int sidechain_version = get_sidechain_version();
 
-		// Enforce deterministic tx keys starting from v15
-		if (m_majorVersion >= HARDFORK_VIEW_TAGS_VERSION) {
-			hash pub, sec;
-			get_tx_keys(pub, sec, spend_pub_key, m_prevId);
-			if ((pub != m_txkeyPub) || (sec != m_txkeySec)) {
+		if (sidechain_version > 1) {
+			hash pub;
+			get_tx_keys(pub, m_txkeySec, m_txkeySecSeed, m_prevId);
+			if (pub != m_txkeyPub) {
 				return __LINE__;
 			}
 		}
+		else {
+			m_txkeySec = m_txkeySecSeed;
+
+			// Enforce deterministic tx keys starting from v15
+			if (m_majorVersion >= HARDFORK_VIEW_TAGS_VERSION) {
+				hash pub, sec;
+				get_tx_keys(pub, sec, spend_pub_key, m_prevId);
+				if ((pub != m_txkeyPub) || (sec != m_txkeySec)) {
+					return __LINE__;
+				}
+			}
+		}
+
+		if (!check_keys(m_txkeyPub, m_txkeySec)) {
+			return __LINE__;
+		}
 
 		READ_BUF(m_parent.h, HASH_SIZE);
 
@@ -317,7 +330,6 @@ int PoolBlock::deserialize(const uint8_t* data, size_t size, const SideChain& si
 		READ_VARINT(m_cumulativeDifficulty.lo);
 		READ_VARINT(m_cumulativeDifficulty.hi);
 
-		const int sidechain_version = get_sidechain_version();
 		if (sidechain_version > 1) {
 			READ_BUF(m_sidechainExtraBuf, sizeof(m_sidechainExtraBuf));
 		}
diff --git a/tests/src/block_template_tests.cpp b/tests/src/block_template_tests.cpp
index f2aaeef..a42195e 100644
--- a/tests/src/block_template_tests.cpp
+++ b/tests/src/block_template_tests.cpp
@@ -60,7 +60,7 @@ TEST(block_template, update)
 	tpl.update(data, mempool, &wallet);
 
 	const PoolBlock* b = tpl.pool_block_template();
-	ASSERT_EQ(b->m_sidechainId, H("d98c48f1137eac26d31ae1d94cce12625c519fc79d1b153035418a1715f6be61"));
+	ASSERT_EQ(b->m_sidechainId, H("e6fa454c10374439dcc9eee3198f6ba17a7a3764510569c3b963b31510b74780"));
 
 	std::vector<uint8_t> blobs;
 	uint64_t height;
@@ -79,7 +79,7 @@ TEST(block_template, update)
 
 	hash blobs_hash;
 	keccak(blobs.data(), static_cast<int>(blobs.size()), blobs_hash.h);
-	ASSERT_EQ(blobs_hash, H("c828b3ef21a28535373aba95ece7429b4abb4c687883722f901eeaf110a9ebaa"));
+	ASSERT_EQ(blobs_hash, H("fd0079d39d1739ded6e710192228276cbaa55eaabde7a26c38f8986709a030e4"));
 
 	// Test 2: mempool with high fee and low fee transactions, it must choose high fee transactions
 	for (uint64_t i = 0; i < 512; ++i) {