diff --git a/SteamTransport/Server.cs b/SteamTransport/Server.cs
index 4facab67..45dd9212 100644
--- a/SteamTransport/Server.cs
+++ b/SteamTransport/Server.cs
@@ -2,6 +2,7 @@
 using Steamworks;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 
 namespace SteamTransport;
 
@@ -102,7 +103,8 @@ public class Server
 	{
 		var ppOutMessages = new IntPtr[Util.MaxMessages];
 
-		foreach (var conn in _conns)
+		// receive can result in disconnect, which modifies the collection. we must copy
+		foreach (var conn in _conns.ToList())
 		{
 			var numMessages = SteamNetworkingSockets.ReceiveMessagesOnConnection(conn, ppOutMessages, ppOutMessages.Length);
 			for (var i = 0; i < numMessages; i++)