diff --git a/external/src/crypto/sha256.c b/external/src/crypto/sha256.c
index d4b05ca..a334210 100644
--- a/external/src/crypto/sha256.c
+++ b/external/src/crypto/sha256.c
@@ -49,7 +49,7 @@ static void sha256_transform(SHA256_CTX *ctx, const uint8_t* data)
 	uint32_t a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
 
 	for (i = 0, j = 0; i < 16; ++i, j += 4)
-		m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
+		m[i] = (((uint32_t)data[j]) << 24) | (((uint32_t)data[j + 1]) << 16) | (((uint32_t)data[j + 2]) << 8) | ((uint32_t)data[j + 3]);
 	for ( ; i < 64; ++i)
 		m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
 
diff --git a/src/merge_mining_client.cpp b/src/merge_mining_client.cpp
index 9507889..0e37619 100644
--- a/src/merge_mining_client.cpp
+++ b/src/merge_mining_client.cpp
@@ -78,6 +78,8 @@ MergeMiningClient::MergeMiningClient(p2pool* pool, const std::string& host, cons
 	}
 	m_timer.data = this;
 
+	uv_rwlock_init_checked(&m_lock);
+
 	err = uv_thread_create(&m_loopThread, loop, this);
 	if (err) {
 		LOGERR(1, "failed to start event loop thread, error " << uv_err_name(err));
@@ -93,13 +95,15 @@ MergeMiningClient::~MergeMiningClient()
 	uv_async_send(&m_shutdownAsync);
 	uv_thread_join(&m_loopThread);
 
+	uv_rwlock_destroy(&m_lock);
+
 	LOGINFO(1, "stopped");
 }
 
 void MergeMiningClient::on_timer()
 {
 	MinerData data = m_pool->miner_data();
-	merge_mining_get_job(data.height, data.prev_id, m_auxWallet, m_auxHash);
+	merge_mining_get_job(data.height, data.prev_id, m_auxWallet, aux_data());
 }
 
 void MergeMiningClient::merge_mining_get_chain_id()
@@ -108,6 +112,8 @@ void MergeMiningClient::merge_mining_get_chain_id()
 
 	JSONRPCRequest::call(m_host, m_port, req, std::string(), m_pool->params().m_socks5Proxy,
 		[this](const char* data, size_t size, double ping) {
+			WriteLock lock(m_lock);
+
 			if (parse_merge_mining_get_chain_id(data, size)) {
 				if (ping > 0.0) {
 					m_ping = ping;
@@ -192,6 +198,8 @@ void MergeMiningClient::merge_mining_get_job(uint64_t height, const hash& prev_i
 
 	JSONRPCRequest::call(m_host, m_port, std::string(buf, s.m_pos), std::string(), m_pool->params().m_socks5Proxy,
 		[this](const char* data, size_t size, double) {
+			WriteLock lock(m_lock);
+
 			parse_merge_mining_get_job(data, size);
 		},
 		[this](const char* data, size_t size, double) {
@@ -260,6 +268,8 @@ bool MergeMiningClient::parse_merge_mining_get_job(const char* data, size_t size
 
 void MergeMiningClient::merge_mining_submit_solution(const std::vector<uint8_t>& blob, const std::vector<hash>& merkle_proof)
 {
+	ReadLock lock(m_lock);
+
 	std::vector<char> buf((m_auxBlob.size() + HASH_SIZE + blob.size()) * 2 + merkle_proof.size() * (HASH_SIZE * 2 + 3) + 256);
 	log::Stream s(buf.data(), buf.size());
 
diff --git a/src/merge_mining_client.h b/src/merge_mining_client.h
index 349a2c3..42d0169 100644
--- a/src/merge_mining_client.h
+++ b/src/merge_mining_client.h
@@ -31,9 +31,9 @@ public:
 
 	void merge_mining_submit_solution(const std::vector<uint8_t>& blob, const std::vector<hash>& merkle_proof);
 
-	FORCEINLINE const hash& aux_id() const { return m_chainID; }
-	FORCEINLINE const hash& aux_data() const { return m_auxHash; }
-	FORCEINLINE const difficulty_type& aux_diff() const { return m_auxDiff; }
+	FORCEINLINE hash aux_id() const { ReadLock lock(m_lock); return m_chainID; }
+	FORCEINLINE hash aux_data() const { ReadLock lock(m_lock); return m_auxHash; }
+	FORCEINLINE difficulty_type aux_diff() const { ReadLock lock(m_lock); return m_auxDiff; }
 
 private:
 	static void loop(void* data);
@@ -52,6 +52,8 @@ private:
 	std::string m_host;
 	uint32_t m_port;
 
+	mutable uv_rwlock_t m_lock;
+
 	std::string m_auxWallet;
 	std::vector<uint8_t> m_auxBlob;
 	hash m_auxHash;