Django sitemap change base url

Solved, I redefined my own get_urls. It works:

class MySitemap(Sitemap):
    changefreq = "never"
    priority = 0.5
    location = ""

    def get_urls(self, site=None, **kwargs):
        site = Site(domain='mydomain.com', name='mydomain.com')
        return super(MySitemap, self).get_urls(site=site, **kwargs)

    def items(self):
        return MyObj.objects.all().order_by('pk')[:1000]

    def lastmod(self, obj):
        return obj.timestamp