diff --git a/TLSharp.Core/MTProto/Crypto/Salt.cs b/TLSharp.Core/MTProto/Crypto/Salt.cs
index 7bda99a..e952ac1 100644
--- a/TLSharp.Core/MTProto/Crypto/Salt.cs
+++ b/TLSharp.Core/MTProto/Crypto/Salt.cs
@@ -10,7 +10,7 @@ namespace TLSharp.Core.MTProto.Crypto
     {
         private int validSince;
         private int validUntil;
-        private ulong salt;
+        private readonly ulong salt;
 
         public Salt(int validSince, int validUntil, ulong salt)
         {
@@ -61,8 +61,8 @@ namespace TLSharp.Core.MTProto.Crypto
 
     public class GetFutureSaltsResponse
     {
-        private ulong requestId;
-        private int now;
+        private readonly ulong requestId;
+        private readonly int now;
         private SaltCollection salts;
 
         public GetFutureSaltsResponse(ulong requestId, int now)
diff --git a/TLSharp.Core/Network/MtProtoPlainSender.cs b/TLSharp.Core/Network/MtProtoPlainSender.cs
index 977d844..eecdd36 100644
--- a/TLSharp.Core/Network/MtProtoPlainSender.cs
+++ b/TLSharp.Core/Network/MtProtoPlainSender.cs
@@ -6,8 +6,8 @@ namespace TLSharp.Core.Network
 {
     public class MtProtoPlainSender
     {
-        private int sequence = 0;
-        private int timeOffset;
+        private readonly int sequence = 0;
+        private readonly int timeOffset;
         private long lastMessageId;
         private Random random;
         private TcpTransport _transport;