Django failing migration - Cannot query "peterson": Must be "User" instance

I'm on Django 1.9, Python 3.6. I made this migration to try and fill in UserProfiles for any users missing them.

But I'm getting the error below.

What's strange is the "user" variable seems to be a User instance.

from __future__ import unicode_literals
from django.db import migrations
from django.contrib.auth.models import User


def create_missing_profiles(apps, schema_editor):
    UserProfile = apps.get_model("myapp", "UserProfile")
    for user in User.objects.all():
        UserProfile.objects.get_or_create(user=user)


class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0004_auto_20170721_0908'),
    ]

    operations = [
        migrations.RunPython(create_missing_profiles),
    ]

Error:

ValueError: Cannot query "peterson": Must be "User" instance.