diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index b0cd89b62..d754adbf2 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -1070,7 +1070,8 @@ void Session::connection_open_finish(ConnectionInfo *info,
   info->state = ConnectionInfo::State::Ready;
   info->created_at = Time::now_cached();
   info->wakeup_at = Time::now_cached() + 10;
-  if (unknown_queries_.size() > 1024) {
+  if (unknown_queries_.size() > MAX_INFLIGHT_QUERIES) {
+    LOG(ERROR) << "With current limits `Too much queries with unknown state` error must be impossible";
     on_session_failed(Status::Error("Too much queries with unknown state"));
     return;
   }
@@ -1311,12 +1312,12 @@ void Session::loop() {
     while (main_connection_.state == ConnectionInfo::State::Ready) {
       if (auth_data_.is_ready(Time::now_cached())) {
         if (need_send_query()) {
-          while (!pending_queries_.empty()) {
+          while (!pending_queries_.empty() && sent_queries_.size() < MAX_INFLIGHT_QUERIES) {
             auto &query = pending_queries_.front();
             connection_send_query(&main_connection_, std::move(query));
             pending_queries_.pop_front();
+            need_flush = true;
           }
-          need_flush = true;
         }
         if (need_send_bind_key()) {
           // send auth.bindTempAuthKey
diff --git a/td/telegram/net/Session.h b/td/telegram/net/Session.h
index 128aa1e4f..b7e292454 100644
--- a/td/telegram/net/Session.h
+++ b/td/telegram/net/Session.h
@@ -157,6 +157,7 @@ class Session final
   bool close_flag_ = false;
 
   static constexpr double ACTIVITY_TIMEOUT = 60 * 5;
+  static constexpr size_t MAX_INFLIGHT_QUERIES = 1024;
 
   struct ContainerInfo {
     size_t ref_cnt;