Django parallel testing: Test processes incorrectly accessing test databases

I have a Django 3.0.8 project running locally, connected to a local PostgreSQL database (postgres:///myapp). When I run python manage.py test, my unit tests run fine; a test database called test_myapp automatically gets created, and it's correctly accessed.

However, when I run python manage.py test --parallel 8, the test fails. I see that 8 cloned databases are correctly generated (test_myapp_1, test_myapp_2,..., test_myapp_8), but I get errors like these:

psycopg2.OperationalError: FATAL:  database "myapp_3" does not exist

It appears that for parallel tests, databases are accessed incorrectly (trying to access the database myapp_N rather than test_myapp_N). I'm trying to figure out if my local config has issues, but this is all I have in my base config:

DATABASES = {
    'default': env.db('DATABASE_URL', default='postgres:///myapp'),
}
DATABASES['default']['ATOMIC_REQUESTS'] = True

Why are my parallel tests processes not accessing their respective cloned test databases correctly?