diff --git a/django/db/models/base.py b/django/db/models/base.py
index a4d5a0d553..0f07d235a9 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -1493,7 +1493,7 @@ class Model(AltersData, metaclass=ModelBase):
                 ):
                     # no value, skip the lookup
                     continue
-                if f in self._meta.pk_fields and not self._state.adding:
+                if f in model_class._meta.pk_fields and not self._state.adding:
                     # no need to check for unique primary key when editing
                     continue
                 lookup_kwargs[str(field_name)] = lookup_value
diff --git a/tests/model_inheritance/tests.py b/tests/model_inheritance/tests.py
index 6b005fcef0..cc333a9ac2 100644
--- a/tests/model_inheritance/tests.py
+++ b/tests/model_inheritance/tests.py
@@ -343,6 +343,11 @@ class ModelInheritanceTests(TestCase):
 
         self.assertEqual(type(MethodOverride.foo), DeferredAttribute)
 
+    def test_full_clean(self):
+        restaurant = Restaurant.objects.create()
+        with self.assertNumQueries(0), self.assertRaises(ValidationError):
+            restaurant.full_clean()
+
 
 class ModelInheritanceDataTests(TestCase):
     @classmethod