diff --git a/librarian_server/stores/local.py b/librarian_server/stores/local.py
index 1eea532..ca7cb2e 100644
--- a/librarian_server/stores/local.py
+++ b/librarian_server/stores/local.py
@@ -126,9 +126,9 @@ def set_for_file(file: Path):
 
                 if self.readonly_after_commit:
                     if file.is_dir():
-                        file.chmod(0o555)
+                        os.chmod(file, 0o555)
                     else:
-                        file.chmod(0o444)
+                        os.chmod(file, 0o444)
 
             # Set for the top-level file.
             set_for_file(resolved_path)