error_page 413 /index.php

I replaced the default 404 setting in my nginx conf file with the above, hoping to redirect my 413 errors as a test for files that are too big.. no dice. Instead I end up here:

https://mydomain.com/!/Workshop/entryUpdate

And Workshop has a yap:

ReflectionException in Container.php line 556:
Method Statamic\Addons\Workshop\WorkshopController::getEntryCreate() does not exist
in Container.php line 556
at ReflectionMethod->__construct(object(WorkshopController), 'getEntryCreate') in Container.php line 556
at Container->getCallReflector(array(object(WorkshopController), 'getEntryCreate')) in Container.php line 536
at Container->getMethodDependencies(array(object(WorkshopController), 'getEntryCreate'), array()) in Container.php line 505
at Container->call(array(object(WorkshopController), 'getEntryCreate'), array()) in Container.php line 604
at Container->callClass('Statamic\Addons\Workshop\[email protected]', array(), null) in Container.php line 502
at Container->call('Statamic\Addons\Workshop\[email protected]', array()) in StatamicController.php line 123
at StatamicController->callControllerMethod('Workshop', 'getEntryCreate', null) in StatamicController.php line 93
at StatamicController->controllerTrigger('Workshop', 'entryCreate')
at call_user_func_array(array(object(StatamicController), 'controllerTrigger'), array('controller' => 'Workshop', 'method' => 'entryCreate')) in Controller.php line 256

I have no idea, honestly.

However, without modifying the default nginx conf like I did above, I end up at the ugly default one! What I want to do is bring 413 errors back to statamic and into my error templates where I've created a pretty 413.html file to tell my users that the upload failed due to the size of it.

Is this the problem? nginx "fails fast" when the client informs it that it's going to send a body larger than the client_max_body_size by sending a 413 response and closing the connection.

Thanks