diff --git a/I2NPProtocol.cpp b/I2NPProtocol.cpp
index dfdd4a2c..aeedfea8 100644
--- a/I2NPProtocol.cpp
+++ b/I2NPProtocol.cpp
@@ -1,4 +1,5 @@
 #include <string.h>
+#include <atomic>
 #include "I2PEndian.h"
 #include <cryptopp/sha.h>
 #include <cryptopp/gzip.h>
@@ -29,7 +30,7 @@ namespace i2p
 		delete msg;
 	}	
 
-	static uint32_t I2NPmsgID = 0; // TODO: create class
+	static std::atomic<uint32_t> I2NPmsgID(0); // TODO: create class
 	void FillI2NPMessageHeader (I2NPMessage * msg, I2NPMessageType msgType, uint32_t replyMsgID)
 	{
 		I2NPHeader * header = msg->GetHeader ();
diff --git a/SSU.cpp b/SSU.cpp
index c7b180ef..0d745663 100644
--- a/SSU.cpp
+++ b/SSU.cpp
@@ -626,7 +626,7 @@ namespace ssu
 		if (!m_DelayedMessages.empty ())
 		{
 			for (auto it :m_DelayedMessages)
-				delete it;
+				DeleteI2NPMessage (it);
 			m_DelayedMessages.clear ();
 		}	
 	}	
diff --git a/SSUData.cpp b/SSUData.cpp
index e363a2bf..46569c5d 100644
--- a/SSUData.cpp
+++ b/SSUData.cpp
@@ -98,7 +98,7 @@ namespace ssu
 					}	
 					else if (fragmentNum < it->second->nextFragmentNum)
 						// duplicate fragment
-						LogPrint ("Duplicate fragment ", fragmentNum, " of message ", msgID, ". Ignored");	
+						LogPrint ("Duplicate fragment ", (int)fragmentNum, " of message ", msgID, ". Ignored");	
 					else
 					{
 						// missing fragment
@@ -108,7 +108,7 @@ namespace ssu
  						
 					if (isLast)
 					{
-						if (!msg)
+						if (!msg)	
 							DeleteI2NPMessage (it->second->msg);
 						delete it->second;
 						m_IncomleteMessages.erase (it);
@@ -116,7 +116,7 @@ namespace ssu
 				}
 				else
 					// TODO:
-					LogPrint ("Unexpected follow-on fragment ", fragmentNum, " of message ", msgID);	
+					LogPrint ("Unexpected follow-on fragment ", (int)fragmentNum, " of message ", msgID);	
 			}
 			else // first fragment
 			{
@@ -156,6 +156,12 @@ namespace ssu
 	void SSUData::Send (i2p::I2NPMessage * msg)
 	{
 		uint32_t msgID = msg->ToSSU ();
+		if (m_SentMessages.count (msgID) > 0)
+		{
+			LogPrint ("SSU message ", msgID, " already sent");
+			DeleteI2NPMessage (msg);
+			return;
+		}		
 		auto fragments = m_SentMessages[msgID];
 		msgID = htobe32 (msgID);	
 		size_t payloadSize = SSU_MTU - sizeof (SSUHeader) - 9; // 9  =  flag + #frg(1) + messageID(4) + frag info (3)