Columns with type `ascii_string` wrongly added to migrations again and again

[fluffycondor]

doctrine/doctrine-migrations-bundle 3.1.1
PostgreSQL 10.18

With the given code

class Foo {
    /**
     * @ORM\Id
     * @ORM\Column(type="ascii_string", unique=true)
     */
    private string $id;
}

I get these lines in my migrations again and again:

final class Version20211011123506 extends AbstractMigration
{
    public function up(Schema $schema): void
    {
        $this->addSql('ALTER TABLE foo ALTER id TYPE VARCHAR(255)');
        $this->addSql('ALTER TABLE foo ALTER id DROP DEFAULT');
    }

    public function down(Schema $schema): void
    {
        $this->addSql('ALTER TABLE foo ALTER id TYPE VARCHAR(255)');
        $this->addSql('ALTER TABLE foo ALTER id DROP DEFAULT');
    }
}

Looks like a bug to me.