diff --git a/libi2pd/SSU2.cpp b/libi2pd/SSU2.cpp
index 871b5b05..296b3817 100644
--- a/libi2pd/SSU2.cpp
+++ b/libi2pd/SSU2.cpp
@@ -219,6 +219,7 @@ namespace transport
 	bool SSU2Server::IsConnectedRecently (const boost::asio::ip::udp::endpoint& ep)
 	{
 		if (!ep.port () || ep.address ().is_unspecified ()) return false;
+		std::lock_guard<std::mutex> l(m_ConnectedRecentlyMutex);
 		auto it = m_ConnectedRecently.find (ep);
 		if (it != m_ConnectedRecently.end ())
 		{	
@@ -234,6 +235,7 @@ namespace transport
 	{
 		if (!ep.port () || ep.address ().is_unspecified () || 
 		    i2p::util::GetSecondsSinceEpoch () > ts + SSU2_HOLE_PUNCH_EXPIRATION) return;
+		std::lock_guard<std::mutex> l(m_ConnectedRecentlyMutex);
 		auto [it, added] = m_ConnectedRecently.try_emplace (ep, ts);
 		if (!added && ts > it->second)
 			it->second = ts; // renew timestamp of existing endpoint
diff --git a/libi2pd/SSU2.h b/libi2pd/SSU2.h
index 31783d58..aac1d02f 100644
--- a/libi2pd/SSU2.h
+++ b/libi2pd/SSU2.h
@@ -194,6 +194,7 @@ namespace transport
 			std::shared_ptr<const i2p::data::IdentityEx> m_PendingTimeOffsetFrom;
 			std::mt19937 m_Rng;
 			std::map<boost::asio::ip::udp::endpoint, uint64_t> m_ConnectedRecently; // endpoint -> last activity time in seconds
+			mutable std::mutex m_ConnectedRecentlyMutex;
 			std::unordered_map<uint32_t, std::pair <std::weak_ptr<SSU2PeerTestSession>, uint64_t > > m_RequestedPeerTests; // nonce->(Alice, timestamp) 
 			std::list<Packet *> m_ReceivedPacketsQueue;
 			mutable std::mutex m_ReceivedPacketsQueueMutex;