diff --git a/td/mtproto/PingConnection.cpp b/td/mtproto/PingConnection.cpp
index 92945ea39..494b2d05d 100644
--- a/td/mtproto/PingConnection.cpp
+++ b/td/mtproto/PingConnection.cpp
@@ -146,7 +146,7 @@ class PingConnectionPingPong final
     LOG(ERROR) << "Unexpected message";
     return Status::OK();
   }
-  void on_message_result_error(uint64 id, int code, BufferSlice descr) final {
+  void on_message_result_error(uint64 id, int code, string message) final {
   }
   void on_message_failed(uint64 id, Status status) final {
   }
diff --git a/td/mtproto/SessionConnection.cpp b/td/mtproto/SessionConnection.cpp
index 7e9409b2f..f875b1ad4 100644
--- a/td/mtproto/SessionConnection.cpp
+++ b/td/mtproto/SessionConnection.cpp
@@ -302,7 +302,7 @@ Status SessionConnection::on_packet(const MsgInfo &info, uint64 req_msg_id, cons
   VLOG(mtproto) << "ERROR " << tag("code", rpc_error.error_code_) << tag("message", rpc_error.error_message_)
                 << tag("req_msg_id", req_msg_id);
   if (req_msg_id != 0) {
-    callback_->on_message_result_error(req_msg_id, rpc_error.error_code_, as_buffer_slice(rpc_error.error_message_));
+    callback_->on_message_result_error(req_msg_id, rpc_error.error_code_, rpc_error.error_message_.str());
   } else {
     LOG(WARNING) << "Receive rpc_error as update: [" << rpc_error.error_code_ << "][" << rpc_error.error_message_
                  << "]";
diff --git a/td/mtproto/SessionConnection.h b/td/mtproto/SessionConnection.h
index bb43dd25f..24bc82103 100644
--- a/td/mtproto/SessionConnection.h
+++ b/td/mtproto/SessionConnection.h
@@ -111,7 +111,7 @@ class SessionConnection final
 
     virtual void on_message_ack(uint64 id) = 0;
     virtual Status on_message_result_ok(uint64 id, BufferSlice packet, size_t original_size) = 0;
-    virtual void on_message_result_error(uint64 id, int code, BufferSlice descr) = 0;
+    virtual void on_message_result_error(uint64 id, int code, string message) = 0;
     virtual void on_message_failed(uint64 id, Status status) = 0;
     virtual void on_message_info(uint64 id, int32 state, uint64 answer_id, int32 answer_size) = 0;
 
diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index 2a7bef7b5..4b0297e9b 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -768,22 +768,22 @@ Status Session::on_message_result_ok(uint64 id, BufferSlice packet, size_t origi
   return Status::OK();
 }
 
-void Session::on_message_result_error(uint64 id, int error_code, BufferSlice message) {
+void Session::on_message_result_error(uint64 id, int error_code, string message) {
   // UNAUTHORIZED
-  if (error_code == 401 && message.as_slice() != CSlice("SESSION_PASSWORD_NEEDED")) {
-    if (auth_data_.use_pfs() && message.as_slice() == CSlice("AUTH_KEY_PERM_EMPTY")) {
+  if (error_code == 401 && message != CSlice("SESSION_PASSWORD_NEEDED")) {
+    if (auth_data_.use_pfs() && message == CSlice("AUTH_KEY_PERM_EMPTY")) {
       LOG(INFO) << "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();
       error_code = 500;
     } else {
-      if (message.as_slice() == CSlice("USER_DEACTIVATED_BAN")) {
+      if (message == CSlice("USER_DEACTIVATED_BAN")) {
         LOG(PLAIN) << "Your account was suspended for suspicious activity. If you think that this is a mistake, please "
                       "write to recover@telegram.org your phone number and other details to recover the account.";
       }
       auth_data_.set_auth_flag(false);
-      G()->shared_config().set_option_string("auth", message.as_slice().str());
+      G()->shared_config().set_option_string("auth", message);
       shared_auth_data_->set_auth_key(auth_data_.get_main_auth_key());
       on_session_failed(Status::OK());
     }
@@ -796,10 +796,10 @@ void Session::on_message_result_error(uint64 id, int error_code, BufferSlice mes
 
   if (error_code < 0) {
     LOG(WARNING) << "Session::on_message_result_error from mtproto " << tag("id", id) << tag("error_code", error_code)
-                 << tag("msg", message.as_slice());
+                 << tag("msg", message);
   } else {
     LOG(DEBUG) << "Session::on_message_result_error " << tag("id", id) << tag("error_code", error_code)
-               << tag("msg", message.as_slice());
+               << tag("msg", message);
   }
   auto it = sent_queries_.find(id);
   if (it == sent_queries_.end()) {
@@ -811,8 +811,7 @@ void Session::on_message_result_error(uint64 id, int error_code, BufferSlice mes
 
   cleanup_container(id, query_ptr);
   mark_as_known(id, query_ptr);
-  query_ptr->query->set_error(Status::Error(error_code, message.as_slice()),
-                              current_info_->connection->get_name().str());
+  query_ptr->query->set_error(Status::Error(error_code, message), current_info_->connection->get_name().str());
   query_ptr->query->set_message_id(0);
   query_ptr->query->cancel_slot_.clear_event();
   return_query(std::move(query_ptr->query));
diff --git a/td/telegram/net/Session.h b/td/telegram/net/Session.h
index 32776fd6d..022aafff4 100644
--- a/td/telegram/net/Session.h
+++ b/td/telegram/net/Session.h
@@ -208,7 +208,7 @@ class Session final
 
   void on_message_ack(uint64 id) final;
   Status on_message_result_ok(uint64 id, BufferSlice packet, size_t original_size) final;
-  void on_message_result_error(uint64 id, int error_code, BufferSlice message) final;
+  void on_message_result_error(uint64 id, int error_code, string message) final;
   void on_message_failed(uint64 id, Status status) final;
 
   void on_message_info(uint64 id, int32 state, uint64 answer_id, int32 answer_size) final;