gistfile1.py

     def get_url_path(self, src):
         from amo.helpers import urlparams, absolutify
-        url = os.path.join(reverse('downloads.file', args=[self.id]),
-                           self.filename)
+        if self.version.addon.is_premium():
+            url = reverse('downloads.watermarked', args=[self.id])
+        else:
+            url = reverse('downloads.file', args=[self.id])
+        url = os.path.join(url, self.filename)
         # Firefox's Add-on Manager needs absolute urls.
         return absolutify(urlparams(url, src=src))