diff --git a/td/telegram/files/FileLoadManager.cpp b/td/telegram/files/FileLoadManager.cpp
index 3b13e60c9..d5c385e39 100644
--- a/td/telegram/files/FileLoadManager.cpp
+++ b/td/telegram/files/FileLoadManager.cpp
@@ -170,6 +170,7 @@ void FileLoadManager::cancel(QueryId query_id) {
   }
   on_error_impl(it->second, Status::Error(-1, "Canceled"));
 }
+
 void FileLoadManager::update_local_file_location(QueryId query_id, const LocalFileLocation &local) {
   if (stop_flag_) {
     return;
diff --git a/td/telegram/files/PartsManager.cpp b/td/telegram/files/PartsManager.cpp
index 80e7f6f38..871945e8e 100644
--- a/td/telegram/files/PartsManager.cpp
+++ b/td/telegram/files/PartsManager.cpp
@@ -311,7 +311,7 @@ Result<Part> PartsManager::start_part() {
 }
 
 Status PartsManager::set_known_prefix(int64 size, bool is_ready) {
-  if (!known_prefix_flag_ || size < static_cast<size_t>(known_prefix_size_)) {
+  if (!known_prefix_flag_ || size < known_prefix_size_ || (size == 0 && !part_status_.empty())) {
     CHECK(is_upload_);
     return Status::Error("FILE_UPLOAD_RESTART");
   }