Migrations fail on production data

When applying the migrations on production data (on beta.thalia.nu) the following error happens:

Operations to perform:
  Apply all migrations: activemembers, admin, announcements, auth, authtoken, contenttypes, documents, education, events, mailinglists, members, merchandise, newsletters, partners, payments, photos, pizzas, pushnotifications, registrations, sessions, sites, thabloid, thaliawebsite
Running migrations:
  Applying documents.0008_0_refactor_documents...Traceback (most recent call last):
  File "/usr/local/lib/python3.5/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
psycopg2.IntegrityError: column "location_en" contains null values

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "./manage.py", line 19, in <module>
    execute_from_command_line(sys.argv)
...
  File "/usr/local/lib/python3.5/site-packages/django/db/backends/utils.py", line 85, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: column "location_en" contains null values