django admin duplicating inlines

For some reason, in my admin site I am seeing a specific inline getting duplicated. I have the following models:

class PageBase(ContentContainer):
  title = models.CharField(max_length=1000)
  slug = models.SlugField()


class PageBanner(models.Model):
    name = models.CharField(max_length=1000)
    page = models.ForeignKey(PageBase)
    banner_images = models.ManyToManyField(BannerImage)

Then in my admin.py I have:

class PageBannerInline(admin.StackedInline):
  model = models.PageBanner
  extra = 1

class PageAdmin(admin.ModelAdmin):
    model = models.Page
    inlines = PageBannerInline

admin.site.register(models.Page, PageAdmin)
admin.site.register(models.PageBanner, PageBannerAdmin) 

For some reason, every time I add a PageBanner to any page in the admin, thus creating another inline for that page, I get anot开发者_开发知识库her extra banner inline on EVERY page(including the one I added on).

So, if I have 4 pages and each page has 1 banner, I will see 3 extra inlines on every page.

What is going on here? This is quickly becoming unmanageable, the inlines take up way too much space.

Here is an image of the inlines:

AFAIK, it's the default behavior of Django to add 3 forms for your inline model, so you can add 3 instances at once. You should be able to change that with the 'extra' attribute:

http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.InlineModelAdmin.extra