diff --git a/AUTHORS b/AUTHORS
index 55211a6790..efc43fa3e8 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -256,7 +256,7 @@ answer newbie questions, and generally made Django that much better:
     Gasper Koren
     Martin Kosír <martin@martinkosir.net>
     Arthur Koziel <http://arthurkoziel.com>
-    Honza Kral <honza.kral@gmail.com>
+    Honza Král <honza.kral@gmail.com>
     Meir Kriheli <http://mksoft.co.il/>
     Bruce Kroeze <http://coderseye.com/>
     krzysiek.pawlik@silvermedia.pl
diff --git a/django/db/models/base.py b/django/db/models/base.py
index 6f90091871..822116054c 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -715,7 +715,7 @@ class Model(object):
             for field_name in unique_check:
                 f = self._meta.get_field(field_name)
                 lookup_value = getattr(self, f.attname)
-                if f.null and lookup_value is None:
+                if lookup_value is None:
                     # no value, skip the lookup
                     continue
                 if f.primary_key and not getattr(self, '_adding', False):
diff --git a/tests/modeltests/validation/test_unique.py b/tests/modeltests/validation/test_unique.py
index 0130208bba..2d67a0a296 100644
--- a/tests/modeltests/validation/test_unique.py
+++ b/tests/modeltests/validation/test_unique.py
@@ -43,18 +43,26 @@ class PerformUniqueChecksTest(unittest.TestCase):
         settings.DEBUG = self._old_debug
         super(PerformUniqueChecksTest, self).tearDown()
 
-    def test_primary_key_unique_check_performed_when_adding(self):
-        """Regression test for #12132"""
-        l = len(connection.queries)
+    def test_primary_key_unique_check_not_performed_when_adding_and_pk_not_specified(self):
+        # Regression test for #12560
+        query_count = len(connection.queries)
         mtv = ModelToValidate(number=10, name='Some Name')
         setattr(mtv, '_adding', True)
         mtv.full_clean()
-        self.assertEqual(l+1, len(connection.queries))
+        self.assertEqual(query_count, len(connection.queries))
+
+    def test_primary_key_unique_check_performed_when_adding_and_pk_specified(self):
+        # Regression test for #12560
+        query_count = len(connection.queries)
+        mtv = ModelToValidate(number=10, name='Some Name', id=123)
+        setattr(mtv, '_adding', True)
+        mtv.full_clean()
+        self.assertEqual(query_count + 1, len(connection.queries))
 
     def test_primary_key_unique_check_not_performed_when_not_adding(self):
-        """Regression test for #12132"""
-        l = len(connection.queries)
+        # Regression test for #12132
+        query_count= len(connection.queries)
         mtv = ModelToValidate(number=10, name='Some Name')
         mtv.full_clean()
-        self.assertEqual(l, len(connection.queries))
+        self.assertEqual(query_count, len(connection.queries))