diff --git a/django/contrib/sites/managers.py b/django/contrib/sites/managers.py
index 8c1cda5417..d49244f78e 100644
--- a/django/contrib/sites/managers.py
+++ b/django/contrib/sites/managers.py
@@ -7,20 +7,14 @@ class CurrentSiteManager(models.Manager):
     def __init__(self, field_name='site'):
         super(CurrentSiteManager, self).__init__()
         self.__field_name = field_name
-
-    def contribute_to_class(self, *args, **kwargs):
-        # This method is overridden purely to check for errors in
-        # self.field_name. We can't do this in __init__() because of
-        # how Managers are implemented -- self.model isn't available
-        # until after contribute_to_class() is called.
-        super(CurrentSiteManager, self).contribute_to_class(*args, **kwargs)
-        try:
-            self.model._meta.get_field(self.__field_name)
-        except FieldDoesNotExist:
-            raise ValueError, "%s couldn't find a field named %s in %s." % \
-                (self.__class__.__name__, self.__field_name, self.model._meta.object_name)
-        self.__lookup = self.__field_name + '__id__exact'
-        del self.__field_name
+        self.__is_validated = False
 
     def get_query_set(self):
-        return super(SiteLimitManager, self).get_query_set().filter(**{self.__lookup: settings.SITE_ID})
+        if not self.__is_validated:
+            try:
+                self.model._meta.get_field(self.__field_name)
+            except FieldDoesNotExist:
+                raise ValueError, "%s couldn't find a field named %s in %s." % \
+                    (self.__class__.__name__, self.__field_name, self.model._meta.object_name)
+            self.__is_validated = True
+        return super(CurrentSiteManager, self).get_query_set().filter(**{self.__field_name + '__id__exact': settings.SITE_ID})