diff --git a/tuf/ngclient/updater.py b/tuf/ngclient/updater.py
index a3477321..08cab467 100644
--- a/tuf/ngclient/updater.py
+++ b/tuf/ngclient/updater.py
@@ -337,6 +337,7 @@ def download_target(
 
             target_file.seek(0)
             with open(filepath, "wb") as destination_file:
+                _lock_file(destination_file)
                 shutil.copyfileobj(target_file, destination_file)
 
         logger.debug("Downloaded target %s", targetinfo.path)