diff --git a/src/p2p_server.cpp b/src/p2p_server.cpp
index ba8fe5d..2ebb05d 100644
--- a/src/p2p_server.cpp
+++ b/src/p2p_server.cpp
@@ -1122,7 +1122,7 @@ void P2PServer::download_missing_blocks()
 		return;
 	}
 
-	std::vector<hash> missing_blocks;
+	unordered_set<hash> missing_blocks;
 	m_pool->side_chain().get_missing_blocks(missing_blocks);
 
 	if (missing_blocks.empty()) {
@@ -1178,7 +1178,7 @@ void P2PServer::download_missing_blocks()
 		const bool result = send(client,
 			[&id, client](uint8_t* buf, size_t buf_size) -> size_t
 			{
-				LOGINFO(5, "sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(client->m_addrString));
+				LOGINFO(5, "[download_missing_blocks] sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(client->m_addrString));
 
 				if (buf_size < 1 + HASH_SIZE) {
 					return 0;
@@ -2368,7 +2368,7 @@ void P2PServer::P2PClient::on_block_notify(const uint8_t* buf)
 		const bool result = server->send(this,
 			[&id, this](uint8_t* buf, size_t buf_size) -> size_t
 			{
-				LOGINFO(5, "sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(m_addrString));
+				LOGINFO(5, "[on_block_notify] sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(m_addrString));
 
 				if (buf_size < 1 + HASH_SIZE) {
 					return 0;
@@ -2546,7 +2546,7 @@ void P2PServer::P2PClient::post_handle_incoming_block(const PoolBlock& block, co
 		const bool result = server->send(this,
 			[this, &id](uint8_t* buf, size_t buf_size) -> size_t
 			{
-				LOGINFO(5, "sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(m_addrString));
+				LOGINFO(5, "[post_handle_incoming_block] sending BLOCK_REQUEST for id = " << id << " to " << static_cast<char*>(m_addrString));
 
 				if (buf_size < 1 + HASH_SIZE) {
 					return 0;
diff --git a/src/side_chain.cpp b/src/side_chain.cpp
index b33fab8..cb6a05c 100644
--- a/src/side_chain.cpp
+++ b/src/side_chain.cpp
@@ -2088,7 +2088,7 @@ void SideChain::prune_old_blocks()
 	}
 }
 
-void SideChain::get_missing_blocks(std::vector<hash>& missing_blocks) const
+void SideChain::get_missing_blocks(unordered_set<hash>& missing_blocks) const
 {
 	missing_blocks.clear();
 
@@ -2100,14 +2100,14 @@ void SideChain::get_missing_blocks(std::vector<hash>& missing_blocks) const
 		}
 
 		if (!b.second->m_parent.empty() && (m_blocksById.find(b.second->m_parent) == m_blocksById.end())) {
-			missing_blocks.push_back(b.second->m_parent);
+			missing_blocks.insert(b.second->m_parent);
 		}
 
 		int num_missing_uncles = 0;
 
 		for (const hash& h : b.second->m_uncles) {
 			if (!h.empty() && (m_blocksById.find(h) == m_blocksById.end())) {
-				missing_blocks.push_back(h);
+				missing_blocks.insert(h);
 
 				// Get no more than 2 first missing uncles at a time from each block
 				// Blocks with more than 2 uncles are very rare and they will be processed in several steps
diff --git a/src/side_chain.h b/src/side_chain.h
index d1f2d33..8746cdc 100644
--- a/src/side_chain.h
+++ b/src/side_chain.h
@@ -52,7 +52,7 @@ public:
 
 	bool add_external_block(PoolBlock& block, std::vector<hash>& missing_blocks);
 	bool add_block(const PoolBlock& block);
-	void get_missing_blocks(std::vector<hash>& missing_blocks) const;
+	void get_missing_blocks(unordered_set<hash>& missing_blocks) const;
 
 	PoolBlock* find_block(const hash& id) const;
 	void watch_mainchain_block(const ChainMain& data, const hash& possible_id);