diff --git a/django/db/models/base.py b/django/db/models/base.py
index e69d59c56f..0b2adc716c 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -14,7 +14,6 @@ from django.dispatch import dispatcher
 from django.utils.datastructures import SortedDict
 from django.utils.functional import curry
 from django.conf import settings
-import re
 import types
 import sys
 import os
@@ -26,14 +25,8 @@ class ModelBase(type):
         if not bases or bases == (object,):
             return type.__new__(cls, name, bases, attrs)
 
-        mod = attrs.pop('__module__')
-
-        # Raise ImportError if this model isn't in INSTALLED_APPS.
-        if re.sub('\.models$', '', mod) not in settings.INSTALLED_APPS:
-            raise ImportError, "INSTALLED_APPS must contain %r in order for you to use this model." % re.sub('\.models$', '', mod)
-
         # Create the class.
-        new_class = type.__new__(cls, name, bases, {'__module__': mod})
+        new_class = type.__new__(cls, name, bases, {'__module__': attrs.pop('__module__')})
         new_class.add_to_class('_meta', Options(attrs.pop('Meta', None)))
         new_class.add_to_class('DoesNotExist', types.ClassType('DoesNotExist', (ObjectDoesNotExist,), {}))
 
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 1693623702..b318599fcc 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -1,3 +1,4 @@
+from django.conf import settings
 from django.db.models.related import RelatedObject
 from django.db.models.fields.related import ManyToManyRel
 from django.db.models.fields import AutoField, FieldDoesNotExist
@@ -35,6 +36,7 @@ class Options:
 
     def contribute_to_class(self, cls, name):
         cls._meta = self
+        self.installed = re.sub('\.models$', '', cls.__module__) in settings.INSTALLED_APPS
         # First, construct the default values for these options.
         self.object_name = cls.__name__
         self.module_name = self.object_name.lower()