diff --git a/td/mtproto/AuthData.cpp b/td/mtproto/AuthData.cpp
index c34e0c16b..3bb0049cf 100644
--- a/td/mtproto/AuthData.cpp
+++ b/td/mtproto/AuthData.cpp
@@ -110,12 +110,13 @@ int64 AuthData::next_message_id(double now) {
   return result;
 }
 
-bool AuthData::is_valid_outbound_msg_id(int64 id, double now) {
+bool AuthData::is_valid_outbound_msg_id(int64 id, double now) const {
   double server_time = get_server_time(now);
   auto id_time = static_cast<double>(id / (1ll << 32));
   return server_time - 300 / 2 < id_time && id_time < server_time + 60 / 2;
 }
-bool AuthData::is_valid_inbound_msg_id(int64 id, double now) {
+
+bool AuthData::is_valid_inbound_msg_id(int64 id, double now) const {
   double server_time = get_server_time(now);
   auto id_time = static_cast<double>(id / (1ll << 32));
   return server_time - 300 < id_time && id_time < server_time + 30;
diff --git a/td/mtproto/AuthData.h b/td/mtproto/AuthData.h
index 334a8e4c2..bf1f50d9c 100644
--- a/td/mtproto/AuthData.h
+++ b/td/mtproto/AuthData.h
@@ -57,7 +57,6 @@ class AuthData {
 
   bool is_ready(double now);
 
-  uint64 session_id_;
   void set_main_auth_key(AuthKey auth_key) {
     main_auth_key_ = std::move(auth_key);
   }
@@ -148,7 +147,7 @@ class AuthData {
     tmp_auth_key_.set_auth_flag(true);
   }
 
-  Slice get_header() {
+  Slice get_header() const {
     if (use_pfs()) {
       return tmp_auth_key_.need_header() ? Slice(header_) : Slice();
     } else {
@@ -170,7 +169,11 @@ class AuthData {
     }
   }
 
+  void set_session_id(uint64 session_id) {
+    session_id_ = session_id;
+  }
   uint64 get_session_id() const {
+    CHECK(session_id_ != 0);
     return session_id_;
   }
 
@@ -204,7 +207,7 @@ class AuthData {
     future_salts_.clear();
   }
 
-  bool is_server_salt_valid(double now) {
+  bool is_server_salt_valid(double now) const {
     return server_salt_.valid_until > get_server_time(now) + 60;
   }
 
@@ -224,9 +227,9 @@ class AuthData {
 
   int64 next_message_id(double now);
 
-  bool is_valid_outbound_msg_id(int64 id, double now);
+  bool is_valid_outbound_msg_id(int64 id, double now) const;
 
-  bool is_valid_inbound_msg_id(int64 id, double now);
+  bool is_valid_inbound_msg_id(int64 id, double now) const;
 
   Status check_packet(int64 session_id, int64 message_id, double now, bool &time_difference_was_updated);
 
@@ -264,6 +267,7 @@ class AuthData {
   int64 last_message_id_ = 0;
   int32 seq_no_ = 0;
   std::string header_;
+  uint64 session_id_ = 0;
 
   std::vector<ServerSalt> future_salts_;
 
diff --git a/td/mtproto/SessionConnection.cpp b/td/mtproto/SessionConnection.cpp
index f835e2503..9ddc54fd8 100644
--- a/td/mtproto/SessionConnection.cpp
+++ b/td/mtproto/SessionConnection.cpp
@@ -499,7 +499,7 @@ Status SessionConnection::on_slice_packet(const MsgInfo &info, Slice packet) {
       return Status::OK();
     } else {
       VLOG(mtproto) << "Got update from " << get_name() << " created in " << (Time::now() - created_at_)
-                    << " in container " << container_id_ << " from session " << auth_data_->session_id_
+                    << " in container " << container_id_ << " from session " << auth_data_->get_session_id()
                     << " with message_id " << info.message_id << ", main_message_id = " << main_message_id_
                     << ", seq_no = " << info.seq_no << " and original size " << info.size;
       return callback_->on_message_result_ok(0, as_buffer_slice(packet), info.size);
@@ -789,7 +789,7 @@ void SessionConnection::destroy_key() {
 std::pair<uint64, BufferSlice> SessionConnection::encrypted_bind(int64 perm_key, int64 nonce, int32 expire_at) {
   int64 temp_key = auth_data_->get_tmp_auth_key().id();
 
-  mtproto_api::bind_auth_key_inner object(nonce, temp_key, perm_key, auth_data_->session_id_, expire_at);
+  mtproto_api::bind_auth_key_inner object(nonce, temp_key, perm_key, auth_data_->get_session_id(), expire_at);
   auto object_storer = create_storer(object);
   auto size = object_storer.size();
   auto object_packet = BufferWriter{size, 0, 0};
diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index 8fa5ed87a..14c33dc4f 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -115,7 +115,6 @@ Session::Session(unique_ptr<Callback> callback, std::shared_ptr<AuthDataShared>
                  bool is_main, bool use_pfs, bool is_cdn, bool need_destroy, const mtproto::AuthKey &tmp_auth_key,
                  std::vector<mtproto::ServerSalt> server_salts)
     : dc_id_(dc_id), is_main_(is_main), is_cdn_(is_cdn) {
-  LOG(INFO) << "Open session: ";
   VLOG(dc) << "Start connection";
   need_destroy_ = need_destroy;
   if (need_destroy) {
@@ -134,7 +133,7 @@ Session::Session(unique_ptr<Callback> callback, std::shared_ptr<AuthDataShared>
   }
   uint64 session_id = 0;
   Random::secure_bytes(reinterpret_cast<uint8 *>(&session_id), sizeof(session_id));
-  auth_data_.session_id_ = session_id;
+  auth_data_.set_session_id(session_id);
   LOG(WARNING) << "Generate new session_id " << session_id << " for " << (use_pfs ? "temp " : "")
                << (is_cdn ? "CDN " : "") << "auth key " << auth_data_.get_auth_key().id() << " for DC" << dc_id;
 
@@ -222,7 +221,7 @@ void Session::send(NetQueryPtr &&query) {
   last_activity_timestamp_ = Time::now();
 
   query->debug("Session: received from SessionProxy");
-  query->set_session_id(auth_data_.session_id_);
+  query->set_session_id(auth_data_.get_session_id());
   VLOG(net_query) << "got query " << query;
   if (query->update_is_ready()) {
     return_query(std::move(query));
@@ -657,7 +656,7 @@ void Session::on_message_result_error(uint64 id, int error_code, BufferSlice mes
   // TODO: some errors shouldn't cause loss of authorizations. Especially when PFS will be used
   if (error_code == 401 && message.as_slice() != CSlice("SESSION_PASSWORD_NEEDED")) {
     if (auth_data_.use_pfs() && message.as_slice() == CSlice("AUTH_KEY_PERM_EMPTY")) {
-      LOG(ERROR) << "Receive AUTH_KEY_PERM_EMPTY in session " << auth_data_.session_id_ << " for auth key "
+      LOG(ERROR) << "Receive AUTH_KEY_PERM_EMPTY in session " << auth_data_.get_session_id() << " for auth key "
                  << auth_data_.get_tmp_auth_key().id();
       auth_data_.drop_tmp_auth_key();
       on_tmp_auth_key_updated();
@@ -822,7 +821,7 @@ void Session::connection_send_query(ConnectionInfo *info, NetQueryPtr &&net_quer
   NetQueryRef invoke_after = net_query->invoke_after();
   if (!invoke_after.empty()) {
     invoke_after_id = invoke_after->message_id();
-    if (invoke_after->session_id() != auth_data_.session_id_ || invoke_after_id == 0) {
+    if (invoke_after->session_id() != auth_data_.get_session_id() || invoke_after_id == 0) {
       net_query->set_error_resend_invoke_after();
       return return_query(std::move(net_query));
     }
@@ -1061,7 +1060,7 @@ void Session::on_handshake_ready(Result<unique_ptr<mtproto::AuthKeyHandshake>> r
         auth_data_.set_tmp_auth_key(std::move(handshake->auth_key));
         on_tmp_auth_key_updated();
       }
-      LOG(WARNING) << "Update auth key in session_id " << auth_data_.session_id_ << " to "
+      LOG(WARNING) << "Update auth key in session_id " << auth_data_.get_session_id() << " to "
                    << auth_data_.get_auth_key().id();
       connection_close(&main_connection_);
       connection_close(&long_poll_connection_);