diff --git a/Lidgren.Network/NetPeer.Send.cs b/Lidgren.Network/NetPeer.Send.cs
index d8fdf3f..ffbad45 100644
--- a/Lidgren.Network/NetPeer.Send.cs
+++ b/Lidgren.Network/NetPeer.Send.cs
@@ -45,6 +45,8 @@ namespace Lidgren.Network
 			if (msg.m_isSent)
 				throw new NetException("This message has already been sent! Use NetPeer.SendMessage() to send to multiple recipients efficiently");
 
+			msg.m_isSent = true;
+
 			int len = msg.LengthBytes;
 			if (len <= recipient.m_currentMTU)
 			{
@@ -91,6 +93,8 @@ namespace Lidgren.Network
 
 			int mtu = GetMTU(recipients);
 
+			msg.m_isSent = true;
+
 			int len = msg.LengthBytes;
 			if (len <= m_configuration.MaximumTransmissionUnit)
 			{
@@ -158,6 +162,7 @@ namespace Lidgren.Network
 				throw new NetException("Unconnected messages too long! Must be shorter than NetConfiguration.MaximumTransmissionUnit (currently " + m_configuration.MaximumTransmissionUnit + ")");
 
 			msg.m_messageType = NetMessageType.Unconnected;
+			msg.m_isSent = true;
 
 			Interlocked.Increment(ref msg.m_recyclingCount);
 			m_unsentUnconnectedMessages.Enqueue(new NetTuple<IPEndPoint, NetOutgoingMessage>(recipient, msg));
@@ -178,6 +183,7 @@ namespace Lidgren.Network
 				throw new NetException("Unconnected messages too long! Must be shorter than NetConfiguration.MaximumTransmissionUnit (currently " + m_configuration.MaximumTransmissionUnit + ")");
 
 			msg.m_messageType = NetMessageType.Unconnected;
+			msg.m_isSent = true;
 
 			Interlocked.Add(ref msg.m_recyclingCount, recipients.Count);
 			foreach(IPEndPoint ep in recipients)
diff --git a/UnitTests/Program.cs b/UnitTests/Program.cs
index 5070f88..47a1936 100644
--- a/UnitTests/Program.cs
+++ b/UnitTests/Program.cs
@@ -27,6 +27,18 @@ namespace UnitTests
 
 			EncryptionTests.Run(peer);
 
+			var om = peer.CreateMessage();
+			peer.SendUnconnectedMessage(om, new IPEndPoint(IPAddress.Loopback, 14242));
+			try
+			{
+				peer.SendUnconnectedMessage(om, new IPEndPoint(IPAddress.Loopback, 14242));
+			}
+			catch (NetException nex)
+			{
+				if (nex.Message != "This message has already been sent! Use NetPeer.SendMessage() to send to multiple recipients efficiently")
+					throw nex;
+			}
+
 			peer.Shutdown("bye");
 
 			// read all message