diff --git a/seal/managers.py b/seal/managers.py
index 50dba70..1589a63 100644
--- a/seal/managers.py
+++ b/seal/managers.py
@@ -8,7 +8,7 @@ class SealedModelIterable(models.query.ModelIterable):
     def __iter__(self):
         objs = super(SealedModelIterable, self).__iter__()
         for obj in objs:
-            obj._state.sealed = True
+            obj.seal()
             yield obj
 
 
diff --git a/seal/models.py b/seal/models.py
index b9f113b..052c520 100644
--- a/seal/models.py
+++ b/seal/models.py
@@ -33,6 +33,9 @@ def __new__(cls, name, bases, attrs):
 class SealableModel(with_metaclass(SealaleModelBase, models.Model)):
     objects = SealableQuerySet.as_manager()
 
+    def seal(self):
+        self._state.sealed = True
+
     class Meta:
         abstract = True
 
diff --git a/tests/models.py b/tests/models.py
index 86a05f2..ebf93e1 100644
--- a/tests/models.py
+++ b/tests/models.py
@@ -1,4 +1,5 @@
 from django.db import models
+from seal.managers import SealableQuerySet
 from seal.models import SealableModel
 
 
@@ -17,3 +18,10 @@ class SeaLion(SealableModel):
 class GreatSeaLion(SeaLion):
     # TODO: add support for auto-generated o2os parent_link and non-parent link o2o.
     sealion_ptr = models.OneToOneField(SeaLion, models.CASCADE, parent_link=True, primary_key=True)
+
+
+class Koala(models.Model):
+    height = models.PositiveIntegerField()
+    weight = models.PositiveIntegerField()
+
+    objects = SealableQuerySet.as_manager()
diff --git a/tests/test_managers.py b/tests/test_managers.py
index d200f1a..3180468 100644
--- a/tests/test_managers.py
+++ b/tests/test_managers.py
@@ -1,7 +1,7 @@
 from django.test import TestCase
 from seal.exceptions import SealedObject
 
-from .models import GreatSeaLion, Location, SeaLion
+from .models import GreatSeaLion, Koala, Location, SeaLion
 
 
 class SealableQuerySetTests(TestCase):
@@ -9,6 +9,7 @@ class SealableQuerySetTests(TestCase):
     def setUpTestData(cls):
         cls.location = Location.objects.create(latitude=51.585474, longitude=156.634331)
         cls.great_sealion = GreatSeaLion.objects.create(height=1, weight=100, location=cls.location)
+        cls.koala = Koala.objects.create(height=1, weight=10)
         cls.sealion = cls.great_sealion.sealion_ptr
         cls.sealion.previous_locations.add(cls.location)
 
@@ -106,3 +107,7 @@ def test_not_reverse_sealed_many_to_many(self):
     def test_sealed_prefetched_reverse_many_to_many(self):
         instance = Location.objects.prefetch_related('previous_visitors').seal().get()
         self.assertSequenceEqual(instance.previous_visitors.all(), [self.sealion])
+
+    def test_improper_usage_raises_error(self):
+        with self.assertRaises(AttributeError):
+            Koala.objects.only('pk').seal().get()
diff --git a/tests/test_models.py b/tests/test_models.py
index 92929fc..fa56cfc 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -7,49 +7,49 @@
 class SealableModelTests(SimpleTestCase):
     def test_sealed_instance_deferred_attribute_access(self):
         instance = SeaLion.from_db('default', ['id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch deferred fields weight on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.weight
 
     def test_sealed_instance_foreign_key_access(self):
         instance = SeaLion.from_db('default', ['id', 'location_id'], [1, 1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch related field location on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.location
 
     def test_sealed_instance_reverse_foreign_key_access(self):
         instance = Location.from_db('default', ['id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch many-to-many field visitors on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.visitors.all()
 
     def test_sealed_instance_parent_link_access(self):
         instance = SeaLion.from_db('default', ['id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch related field greatsealion on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.greatsealion
 
     def test_sealed_instance_reverse_parent_link_access(self):
         instance = GreatSeaLion.from_db('default', ['sealion_ptr_id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch related field sealion_ptr on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.sealion_ptr
 
     def test_sealed_instance_m2m_access(self):
         instance = SeaLion.from_db('default', ['id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch many-to-many field previous_locations on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.previous_locations.all()
 
     def test_sealed_instance_reverse_m2m_access(self):
         instance = Location.from_db('default', ['id'], [1])
-        instance._state.sealed = True
+        instance.seal()
         message = "Cannot fetch many-to-many field previous_visitors on a sealed object."
         with self.assertRaisesMessage(SealedObject, message):
             instance.previous_visitors.all()