Django-filer is not able to create the model. What can I do?

When makemigrations error

super(FilerFileField, self).__init__(**kwargs)
TypeError: __init__() missing 1 required positional argument: 'on_delete'

Here is the model:
from django.db import models
from filer.fields.image import FilerImageField 

class Book(models.Model):
 title = models.CharField(max_length=200)
 cover = FilerImageField(null=True, blank=True, related_name="book_covers")
April 4th 20 at 00:40
1 answer
April 4th 20 at 00:42

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