diff --git a/README.md b/README.md
index 2c8efa8..a3eae1b 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,8 @@ Building
 
 A managed assembly can be built using any available compiling platform that supports C# 3.0 or higher.
 
+Must define `VALVE_CALLBACK_PACK_SMALL` on Linux/Apple/FreeBSD, or `VALVE_CALLBACK_PACK_LARGE` on other platforms.
+
 Define `VALVESOCKETS_SPAN` to enable support for Span. Please, follow [these steps](https://github.com/nxrighthere/ValveSockets-CSharp/issues/3#issuecomment-491916163) to enable fast access to native memory blocks and improve performance.
 
 Usage
diff --git a/ValveSockets.cs b/ValveSockets.cs
index 7d17cde..b0416ea 100644
--- a/ValveSockets.cs
+++ b/ValveSockets.cs
@@ -257,7 +257,7 @@ public enum Result {
 		WGNetworkSendExceeded = 110
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	[StructLayout(LayoutKind.Sequential, Pack = 1)]
 	public struct Address : IEquatable<Address> {
 		[MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
 		public byte[] ip;
@@ -289,7 +289,7 @@ public bool Equals(Address other) {
 		}
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	[StructLayout(LayoutKind.Sequential, Pack = 8)]
 	public struct Configuration {
 		public ConfigurationValue value;
 		public ConfigurationDataType dataType;
@@ -310,7 +310,18 @@ public struct ConfigurationData {
 		}
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	static class StructConst
+	{
+#if VALVE_CALLBACK_PACK_SMALL
+		public const int PACK_SIZE = 4;
+#elif VALVE_CALLBACK_PACK_LARGE
+		public const int PACK_SIZE = 8;
+#else
+		#error "Not define VALVE_CALLBACK_PACK_SMALL(Linux/Apple/FreeBSD) or VALVE_CALLBACK_PACK_LARGE(Anything else.)"
+#endif
+	}
+	
+	[StructLayout(LayoutKind.Sequential, Pack = StructConst.PACK_SIZE)]
 	public struct StatusInfo {
 		private const int callback = Library.socketsCallbacks + 1;
 		public Connection connection;
@@ -318,7 +329,7 @@ public struct StatusInfo {
 		private ConnectionState oldState;
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	[StructLayout(LayoutKind.Sequential, Pack = StructConst.PACK_SIZE)]
 	public struct ConnectionInfo {
 		public NetworkingIdentity identity;
 		public long userData;
@@ -333,11 +344,12 @@ public struct ConnectionInfo {
 		public string endDebug;
 		[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
 		public string connectionDescription;
-		[MarshalAs(UnmanagedType.ByValArray, SizeConst = 64)]
+		public int flags;
+		[MarshalAs(UnmanagedType.ByValArray, SizeConst = 63)]
 		private uint[] reserved;
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	[StructLayout(LayoutKind.Sequential, Pack = StructConst.PACK_SIZE)]
 	public struct ConnectionStatus {
 		public ConnectionState state;
 		public int ping;
@@ -356,7 +368,7 @@ public struct ConnectionStatus {
 		private uint[] reserved;
 	}
 
-	[StructLayout(LayoutKind.Explicit, Size = 136)]
+	[StructLayout(LayoutKind.Explicit, Size = 136, Pack = 1)]
 	public struct NetworkingIdentity {
 		[FieldOffset(0)]
 		public IdentityType type;
@@ -376,7 +388,7 @@ public void SetSteamID(ulong steamID) {
 		}
 	}
 
-	[StructLayout(LayoutKind.Sequential)]
+	[StructLayout(LayoutKind.Sequential, Pack = 8)]
 	public struct NetworkingMessage {
 		public IntPtr data;
 		public int length;
@@ -390,6 +402,8 @@ public struct NetworkingMessage {
 		public int channel;
 		public int flags;
 		public long userData;
+		public ushort idxLane;
+		public ushort pad1__;
 
 		public void CopyTo(byte[] destination) {
 			if (destination == null)