diff --git a/tests/postgres_tests/test_hstore.py b/tests/postgres_tests/test_hstore.py
index ed88e2f..8c4172f 100644
--- a/tests/postgres_tests/test_hstore.py
+++ b/tests/postgres_tests/test_hstore.py
@@ -114,6 +114,13 @@ class TestQuerying(PostgresSQLTestCase):
             self.objs[:3]
         )
 
+    def test_key_isnull(self):
+        obj = HStoreModel.objects.create(field={'a': None})
+        self.assertSequenceEqual(
+            HStoreModel.objects.filter(field__a__isnull=True),
+            [obj]
+        )
+
 
 class TestSerialization(PostgresSQLTestCase):
     test_data = '[{"fields": {"field": "{\\"a\\": \\"b\\"}"}, "model": "postgres_tests.hstoremodel", "pk": null}]'