Question: While updating an old Wagtail website to the current version, I encounter this error, in admin/panels/group.py line 74: AttributeError: 'StreamField' object has no attribute 'bind_to_model' Since this is apparently in the Wagtail software as distributed, I am quite confused.  The full traceback is as follows: Exception in thread django-main-thread: Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 1041, in _bootstrap_inner self.run() ~~~~~~~~^^ File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/threading.py", line 992, in run self._target(*self._args, **self._kwargs) ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/utils/autoreload.py", line 64, in wrapper fn(*args, **kwargs) ~~^^^^^^^^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/management/commands/runserver.py", line 134, in inner_run self.check(display_num_errors=True) ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/management/base.py", line 486, in check all_issues = checks.run_checks( app_configs=app_configs, ...<2 lines>... databases=databases, ) File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/core/checks/registry.py", line 88, in run_checks new_errors = check(app_configs=app_configs, databases=databases) File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/checks.py", line 69, in get_form_class_check edit_handler = cls.get_edit_handler() File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/utils/decorators.py", line 54, in __call__ return self.value ^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/django/utils/functional.py", line 47, in __get__ res = instance.__dict__[self.name] = self.func(instance) ~~~~~~~~~^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/utils/decorators.py", line 50, in value return self.fn(self.cls) ~~~~~~~^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/page_utils.py", line 73, in _get_page_edit_handler return edit_handler.bind_to_model(cls) ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/base.py", line 146, in bind_to_model new.on_model_bound() ~~~~~~~~~~~~~~~~~~^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/group.py", line 74, in on_model_bound self.children = [child.bind_to_model(self.model) for child in self.children] ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/base.py", line 146, in bind_to_model new.on_model_bound() ~~~~~~~~~~~~~~~~~~^^ File "/Users/mike/.virtualenvs/sdenv/lib/python3.13/site-packages/wagtail/admin/panels/group.py", line 74, in on_model_bound self.children = [child.bind_to_model(self.model) for child in self.children] ^^^^^^^^^^^^^^^^^^^ AttributeError: 'StreamField' object has no attribute 'bind_to_model' 

Answer: The error indicates that you have a StreamField object inside a panels definition such as content_panels. This isn't valid - it should only contain panel objects such as FieldPanel. As part of the Wagtail 2.x to 6.x upgrade process, you would have to replace any instances of StreamFieldPanel with a plain FieldPanel - my best guess is that you made a mistake while doing this, and changed StreamFieldPanel to StreamField instead.