diff --git a/td/telegram/files/FileLoader.cpp b/td/telegram/files/FileLoader.cpp
index 9ebd6f8e0..3bdeaa6c7 100644
--- a/td/telegram/files/FileLoader.cpp
+++ b/td/telegram/files/FileLoader.cpp
@@ -54,7 +54,12 @@ void FileLoader::update_local_file_location(const LocalFileLocation &local) {
     return;
   }
   auto prefix_info = r_prefix_info.move_as_ok();
-  parts_manager_.set_known_prefix(narrow_cast<size_t>(prefix_info.size), prefix_info.is_ready);
+  auto status = parts_manager_.set_known_prefix(narrow_cast<size_t>(prefix_info.size), prefix_info.is_ready);
+  if (status.is_error()) {
+    on_error(std::move(status));
+    stop_flag_ = true;
+    return;
+  }
   loop();
 }
 
@@ -67,11 +72,12 @@ void FileLoader::start_up() {
   }
   auto file_info = r_file_info.ok();
   auto size = file_info.size;
+  auto expected_size = std::max(size, file_info.expected_size);
   bool is_size_final = file_info.is_size_final;
   auto part_size = file_info.part_size;
   auto &ready_parts = file_info.ready_parts;
   auto use_part_count_limit = file_info.use_part_count_limit;
-  auto status = parts_manager_.init(size, is_size_final, part_size, ready_parts, use_part_count_limit);
+  auto status = parts_manager_.init(size, expected_size, is_size_final, part_size, ready_parts, use_part_count_limit);
   if (status.is_error()) {
     on_error(std::move(status));
     stop_flag_ = true;
diff --git a/td/telegram/files/FileLoader.h b/td/telegram/files/FileLoader.h
index 7a4d35d70..10d97fab6 100644
--- a/td/telegram/files/FileLoader.h
+++ b/td/telegram/files/FileLoader.h
@@ -48,6 +48,7 @@ class FileLoader : public FileLoaderActor {
   };
   struct FileInfo {
     int64 size;
+    int64 expected_size = 0;
     bool is_size_final;
     int32 part_size;
     std::vector<int> ready_parts;
diff --git a/td/telegram/files/FileManager.cpp b/td/telegram/files/FileManager.cpp
index eb5aabaa5..8b6ba545a 100644
--- a/td/telegram/files/FileManager.cpp
+++ b/td/telegram/files/FileManager.cpp
@@ -639,6 +639,9 @@ Result<FileId> FileManager::register_file(FileData data, FileLocationSource file
     if (status.is_error()) {
       LOG(WARNING) << "Invalid local location: " << status << " from " << source;
       data.local_ = LocalFileLocation();
+      if (data.remote_.type() == RemoteFileLocation::Type::Partial) {
+        data.remote_ = {};
+      }
 
       if (!has_remote && !has_generate) {
         return std::move(status);
@@ -2178,7 +2181,7 @@ void FileManager::on_error_impl(FileNode *node, FileManager::Query::Type type, b
                  << ". File type is " << file_type_name[static_cast<int32>(FileView(node).get_type())];
     if (status.code() == 0) {
       // Remove partial locations
-      if (node->local_.type() == LocalFileLocation::Type::Partial) {
+      if (node->local_.type() == LocalFileLocation::Type::Partial && status.message() != "FILE_UPLOAD_RESTART") {
         LOG(INFO) << "Unlink file " << node->local_.partial().path_;
         unlink(node->local_.partial().path_).ignore();
         node->set_local_location(LocalFileLocation(), 0);
diff --git a/td/telegram/files/FileUploader.cpp b/td/telegram/files/FileUploader.cpp
index 26f16fda3..635e5c893 100644
--- a/td/telegram/files/FileUploader.cpp
+++ b/td/telegram/files/FileUploader.cpp
@@ -223,7 +223,8 @@ Result<std::pair<NetQueryPtr, bool>> FileUploader::start_part(Part part, int32 p
 
   NetQueryPtr net_query;
   if (big_flag_) {
-    auto query = telegram_api::upload_saveBigFilePart(file_id_, part.id, part_count, std::move(bytes));
+    auto query =
+        telegram_api::upload_saveBigFilePart(file_id_, part.id, local_is_ready_ ? part_count : -1, std::move(bytes));
     net_query = G()->net_query_creator().create(create_storer(query), DcId::main(), NetQuery::Type::Upload,
                                                 NetQuery::AuthFlag::On, NetQuery::GzipFlag::Off);
   } else {
diff --git a/td/telegram/files/PartsManager.cpp b/td/telegram/files/PartsManager.cpp
index eae9ddd15..47e85dc2a 100644
--- a/td/telegram/files/PartsManager.cpp
+++ b/td/telegram/files/PartsManager.cpp
@@ -16,6 +16,14 @@
 
 namespace td {
 /*** PartsManager ***/
+
+namespace {
+int64 calc_parts_count(int64 size, int64 part_size) {
+  CHECK(part_size != 0);
+  return (size + part_size - 1) / part_size;
+}
+}  // namespace
+
 Status PartsManager::init_known_prefix(int64 known_prefix, size_t part_size, const std::vector<int> &ready_parts) {
   known_prefix_flag_ = true;
   known_prefix_size_ = known_prefix;
@@ -32,6 +40,14 @@ Status PartsManager::init_no_size(size_t part_size, const std::vector<int> &read
     part_size_ = part_size;
   } else {
     part_size_ = 32 * (1 << 10);
+    while (use_part_count_limit_ && calc_parts_count(expected_size_, part_size_) > MAX_PART_COUNT) {
+      part_size_ *= 2;
+      CHECK(part_size_ <= MAX_PART_SIZE);
+    }
+    // just in case if expected_size_ is wrong
+    if (part_size_ < MAX_PART_SIZE) {
+      part_size_ *= 2;
+    }
   }
   part_count_ = 0;
   if (known_prefix_flag_) {
@@ -44,40 +60,42 @@ Status PartsManager::init_no_size(size_t part_size, const std::vector<int> &read
   return Status::OK();
 }
 
-Status PartsManager::init(int64 size, bool is_size_final, size_t part_size, const std::vector<int> &ready_parts,
-                          bool use_part_count_limit) {
+Status PartsManager::init(int64 size, int64 expected_size, bool is_size_final, size_t part_size,
+                          const std::vector<int> &ready_parts, bool use_part_count_limit) {
+  CHECK(expected_size >= size);
   use_part_count_limit_ = use_part_count_limit;
+  expected_size_ = expected_size;
+  if (expected_size_ > MAX_FILE_SIZE) {
+    return Status::Error("Too big file");
+  }
   if (!is_size_final) {
     return init_known_prefix(size, part_size, ready_parts);
   }
   if (size == 0) {
     return init_no_size(part_size, ready_parts);
   }
-  if (size > MAX_FILE_SIZE) {
-    return Status::Error("Too big file");
-  }
   CHECK(size > 0) << tag("size", size);
   unknown_size_flag_ = false;
   size_ = size;
 
   if (part_size != 0) {
     part_size_ = part_size;
-    if (use_part_count_limit_ && (size_ + part_size_ - 1) / part_size_ > MAX_PART_COUNT) {
+    if (use_part_count_limit_ && calc_parts_count(expected_size_, part_size_) > MAX_PART_COUNT) {
       return Status::Error("FILE_UPLOAD_RESTART");
     }
   } else {
     // TODO choose part_size_ depending on size
     part_size_ = 64 * (1 << 10);
-    while (use_part_count_limit && (size_ + part_size_ - 1) / part_size_ > MAX_PART_COUNT) {
+    while (use_part_count_limit && calc_parts_count(expected_size_, part_size_) > MAX_PART_COUNT) {
       part_size_ *= 2;
       CHECK(part_size_ <= MAX_PART_SIZE);
     }
   }
   CHECK(1 <= size_) << tag("size_", size_);
-  CHECK(!use_part_count_limit || (size_ + part_size_ - 1) / part_size_ <= MAX_PART_COUNT)
-      << tag("size_", size_) << tag("is_size_final", is_size_final) << tag("part_size_", part_size_)
-      << tag("ready_parts", ready_parts.size());
-  part_count_ = static_cast<int>((size + part_size_ - 1) / part_size_);
+  CHECK(!use_part_count_limit || calc_parts_count(expected_size_, part_size_) <= MAX_PART_COUNT)
+      << tag("size_", size_) << tag("expected_size", size_) << tag("is_size_final", is_size_final)
+      << tag("part_size_", part_size_) << tag("ready_parts", ready_parts.size());
+  part_count_ = static_cast<int>(calc_parts_count(size_, part_size_));
 
   init_common(ready_parts);
   return Status::OK();
@@ -147,14 +165,15 @@ Result<Part> PartsManager::start_part() {
   return get_part(id);
 }
 
-void PartsManager::set_known_prefix(size_t size, bool is_ready) {
+Status PartsManager::set_known_prefix(size_t size, bool is_ready) {
   CHECK(known_prefix_flag_);
   CHECK(size >= static_cast<size_t>(known_prefix_size_));
   known_prefix_size_ = narrow_cast<int64>(size);
+  expected_size_ = std::max(known_prefix_size_, expected_size_);
 
   CHECK(static_cast<size_t>(part_count_) == part_status_.size());
   if (is_ready) {
-    part_count_ = static_cast<int>((size + part_size_ - 1) / part_size_);
+    part_count_ = static_cast<int>(calc_parts_count(size, part_size_));
 
     size_ = narrow_cast<int64>(size);
     unknown_size_flag_ = false;
@@ -164,6 +183,10 @@ void PartsManager::set_known_prefix(size_t size, bool is_ready) {
   CHECK(static_cast<size_t>(part_count_) >= part_status_.size())
       << size << " " << is_ready << " " << part_count_ << " " << part_size_ << " " << part_status_.size();
   part_status_.resize(part_count_);
+  if (use_part_count_limit_ && calc_parts_count(expected_size_, part_size_) > MAX_PART_COUNT) {
+    return Status::Error("FILE_UPLOAD_RESTART");
+  }
+  return Status::OK();
 }
 
 Status PartsManager::on_part_ok(int32 id, size_t part_size, size_t actual_size) {
diff --git a/td/telegram/files/PartsManager.h b/td/telegram/files/PartsManager.h
index 91ba116fd..26c31d517 100644
--- a/td/telegram/files/PartsManager.h
+++ b/td/telegram/files/PartsManager.h
@@ -20,8 +20,8 @@ struct Part {
 
 class PartsManager {
  public:
-  Status init(int64 size, bool is_size_final, size_t part_size, const std::vector<int> &ready_parts,
-              bool use_part_count_limit) TD_WARN_UNUSED_RESULT;
+  Status init(int64 size, int64 expected_size, bool is_size_final, size_t part_size,
+              const std::vector<int> &ready_parts, bool use_part_count_limit) TD_WARN_UNUSED_RESULT;
   bool ready();
   bool unchecked_ready();
   Status finish() TD_WARN_UNUSED_RESULT;
@@ -30,7 +30,7 @@ class PartsManager {
   Result<Part> start_part() TD_WARN_UNUSED_RESULT;
   Status on_part_ok(int32 id, size_t part_size, size_t actual_size) TD_WARN_UNUSED_RESULT;
   void on_part_failed(int32 id);
-  void set_known_prefix(size_t size, bool is_ready);
+  Status set_known_prefix(size_t size, bool is_ready);
   void set_need_check();
   void set_checked_prefix_size(int64 size);
 
@@ -58,6 +58,7 @@ class PartsManager {
   int64 known_prefix_size_;
 
   int64 size_;
+  int64 expected_size_;
   int64 min_size_;
   int64 max_size_;
   bool unknown_size_flag_;