Assigning ForeignKey fields in migrations

[Odero]

I've created the migration below which is failing. It seems like the same issue discussed and resolved here https://code.djangoproject.com/ticket/24282

def generate_invoices(apps, schema_editor):
    Payment = apps.get_model('finance', 'Payment')
    Invoice = apps.get_model('finance', 'Invoice')
    User = apps.get_model('accounts', 'User')

    payment = Payment.objects.last()

    invoice = Invoice(
        client=payment.user),
        status=5
    )
    invoice.save()

Also tried

    invoice = Invoice(
        client=User.objects.get(pk=payment.user.pk),
        status=5
    )

In both cases I get the error:

Cannot assign "<User: Some Client>": "Invoice.client" must be a "User" instance.