id summary reporter owner description type status component version severity resolution keywords cc stage has_patch needs_docs needs_tests needs_better_patch easy ui_ux 28159 Using InlineFormset.save_as_new crashes in Django 1.11 Alexander Kavanaugh nobody "Django 1.11 marks multipart POST data as immutable: 4a246a02bdcbc13b15480c014f51cb0682af7c1e (#17235) . This causes an issue with the private `save_as_new` feature in InlineFormsets: the set code in the conditional block in [https://github.com/django/django/blob/05098fa4494e66e1d3750d7f4821f7b3114693b9/django/forms/models.py#L886 BaseInlineFormSet._construct_form()] now raises `AttributeError` because the data it's attempting to change is marked as immutable. To restore previous behavior, [https://github.com/django/django/pull/8448 this pull request] turns off the immutability flag on the form data while the save_as_new functionality runs and turns immutability back on when the mutation code is complete. Note that the mutable flag isn't set if there is no data, hence the `hasattr` code. " Bug closed Forms 1.11 Release blocker fixed inlineformset,save_as_new Accepted 1 0 0 0 0 0