diff --git a/td/telegram/MessagesManager.cpp b/td/telegram/MessagesManager.cpp
index 82e6491c..d77a11e1 100644
--- a/td/telegram/MessagesManager.cpp
+++ b/td/telegram/MessagesManager.cpp
@@ -9584,7 +9584,7 @@ void MessagesManager::recalc_unread_count(FolderId folder_id) {
   int32 dialog_muted_count = 0;
   int32 dialog_marked_count = 0;
   int32 dialog_muted_marked_count = 0;
-  for (auto &dialog_date : list.ordered_server_dialogs_) {
+  for (const auto &dialog_date : list.ordered_server_dialogs_) {
     auto dialog_id = dialog_date.get_dialog_id();
     Dialog *d = get_dialog(dialog_id);
     CHECK(d != nullptr);
@@ -27988,6 +27988,14 @@ bool MessagesManager::set_dialog_order(Dialog *d, int64 new_order, bool need_sen
   bool is_removed_from_folder = new_order == DEFAULT_ORDER;
   bool is_added_to_folder = d->order == DEFAULT_ORDER;
 
+  if (is_removed_from_folder) {
+    list.in_memory_total_count_--;
+  } else if (is_added_to_folder) {
+    list.in_memory_total_count_++;
+  }
+  CHECK(static_cast<int32>(list.ordered_dialogs_.size()) <= list.in_memory_total_count_);
+  CHECK(static_cast<size_t>(list.in_memory_total_count_) <= list.ordered_server_dialogs_.size());
+
   if (!is_loaded_from_database && had_unread_counter != has_unread_counter && !td_->auth_manager_->is_bot()) {
     auto unread_count = d->server_unread_count + d->local_unread_count;
     const char *change_source = had_unread_counter ? "on_dialog_leave" : "on_dialog_join";
diff --git a/td/telegram/MessagesManager.h b/td/telegram/MessagesManager.h
index 73468fd5..07cdf6a3 100644
--- a/td/telegram/MessagesManager.h
+++ b/td/telegram/MessagesManager.h
@@ -1213,9 +1213,10 @@ class MessagesManager : public Actor {
     int32 unread_dialog_muted_count_ = 0;
     int32 unread_dialog_marked_count_ = 0;
     int32 unread_dialog_muted_marked_count_ = 0;
+    int32 in_memory_total_count_ = 0;
 
-    std::set<DialogDate> ordered_dialogs_;
-    std::set<DialogDate> ordered_server_dialogs_;
+    std::set<DialogDate> ordered_dialogs_;         // all dialogs with date <= last_dialog_date_
+    std::set<DialogDate> ordered_server_dialogs_;  // all known dialogs, including with default order
 
     // date of last dialog in the dialog list
     // last_dialog_date_ == min(last_server_dialog_date_, last_secret_chat_dialog_date_)