diff --git a/common/djangoapps/student/models.py b/common/djangoapps/student/models.py
index fc4f46de1c..6cc3662725 100644
--- a/common/djangoapps/student/models.py
+++ b/common/djangoapps/student/models.py
@@ -121,7 +121,6 @@ class AnonymousUserId(models.Model):
     user = models.ForeignKey(User, db_index=True)
     anonymous_user_id = models.CharField(unique=True, max_length=32)
     course_id = CourseKeyField(db_index=True, max_length=255, blank=True)
-    unique_together = (user, course_id)
 
 
 def anonymous_id_for_user(user, course_id, save=True):
@@ -159,22 +158,11 @@ def anonymous_id_for_user(user, course_id, save=True):
         return digest
 
     try:
-        anonymous_user_id, __ = AnonymousUserId.objects.get_or_create(
-            defaults={'anonymous_user_id': digest},
+        AnonymousUserId.objects.get_or_create(
             user=user,
-            course_id=course_id
+            course_id=course_id,
+            anonymous_user_id=digest,
         )
-        if anonymous_user_id.anonymous_user_id != digest:
-            log.error(
-                u"Stored anonymous user id %(anonymous_user_id)r for "
-                u"user %(user)r in course %(course_id)r doesn't match "
-                u"computed id %(digest)r", {
-                    "anonymous_user_id": anonymous_user_id.anonymous_user_id,
-                    "user": user,
-                    "course_id": course_id,
-                    "digest": digest,
-                }
-            )
     except IntegrityError:
         # Another thread has already created this entry, so
         # continue
diff --git a/common/djangoapps/student/tests/tests.py b/common/djangoapps/student/tests/tests.py
index e61fc82403..73ff1bd788 100644
--- a/common/djangoapps/student/tests/tests.py
+++ b/common/djangoapps/student/tests/tests.py
@@ -12,7 +12,7 @@ import ddt
 from django.conf import settings
 from django.contrib.auth.models import User, AnonymousUser
 from django.core.urlresolvers import reverse
-from django.test import TestCase
+from django.test import TestCase, override_settings
 from django.test.client import Client
 from edx_oauth2_provider.tests.factories import ClientFactory
 import httpretty
@@ -945,7 +945,7 @@ class AnonymousLookupTable(ModuleStoreTestCase):
     def setUp(self):
         super(AnonymousLookupTable, self).setUp()
         self.course = CourseFactory.create()
-        self.user = UserFactory()
+        self.user = UserFactory.create()
         CourseModeFactory.create(
             course_id=self.course.id,
             mode_slug='honor',
@@ -974,6 +974,18 @@ class AnonymousLookupTable(ModuleStoreTestCase):
         self.assertEqual(self.user, real_user)
         self.assertEqual(anonymous_id, anonymous_id_for_user(self.user, course2.id, save=False))
 
+    def test_secret_key_changes(self):
+        """Test that a new anonymous id is returned when the secret key changes."""
+        CourseEnrollment.enroll(self.user, self.course.id)
+        anonymous_id = anonymous_id_for_user(self.user, self.course.id)
+        with override_settings(SECRET_KEY='some_new_and_totally_secret_key'):
+            # Recreate user object to clear cached anonymous id.
+            self.user = User.objects.get(pk=self.user.id)
+            new_anonymous_id = anonymous_id_for_user(self.user, self.course.id)
+            self.assertNotEqual(anonymous_id, new_anonymous_id)
+            self.assertEqual(self.user, user_by_anonymous_id(anonymous_id))
+            self.assertEqual(self.user, user_by_anonymous_id(new_anonymous_id))
+
 
 @attr(shard=3)
 @httpretty.activate