Django easy-thumbnails getting weird naming with duplicate extensions

I'm using easy-thumbnails, the original file is saved correctly but the thumbnails are being saved with a duplicate file extension:

11.jpg
11.jpg.100x100_q85.jpg

I would like the thumbnails to be named like this:

11.100x100_q85.jpg

My model looks like this:

def image_filename(instance, filename):
    folder = 'posts/image'
    _, ext = os.path.splitext(filename)
    new_name = str(instance.id) + ext
    return os.path.join(folder, new_name)


class Post(models.Model):
    name = models.CharField(max_length=255, unique=True)
    image = ThumbnailerImageField(upload_to=image_filename, null=True, blank=True)

Since im using Django Rest Framework I created a serializer following this post: Django easy-thumbnails serialize with Django Rest Framework

class ThumbnailSerializer(serializers.ImageField):
    def __init__(self, alias, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.read_only = True
        self.alias = alias

    def to_representation(self, value):
        if not value:
            return None

        url = thumbnail_url(value, self.alias)
        request = self.context.get('request', None)
        if request is not None:
            return request.build_absolute_uri(url)

        return url

Does anyone know how I can get the correct naming on my thumbnails?

Thanks!

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