Obvious, isn't it?
  --md@hudora.de

Index: django/contrib/comments/models.py
===================================================================
--- django/contrib/comments/models.py	(revision 3797)
+++ django/contrib/comments/models.py	(working copy)
@@ -64,7 +64,7 @@
 class Comment(models.Model):
     user = models.ForeignKey(User, raw_id_admin=True)
     content_type = models.ForeignKey(ContentType)
-    object_id = models.IntegerField(_('object ID'))
+    object_id = models.CharField(_('object ID'), maxlength=255)
     headline = models.CharField(_('headline'), maxlength=255, blank=True)
     comment = models.TextField(_('comment'), maxlength=3000)
     rating1 = models.PositiveSmallIntegerField(_('rating #1'), blank=True, null=True)