diff --git a/tests/test_multidict.py b/tests/test_multidict.py
index 10cf2025a7b..c31e1f470ab 100644
--- a/tests/test_multidict.py
+++ b/tests/test_multidict.py
@@ -180,7 +180,7 @@ def test_sub(self):
 
     def test_xor(self):
         d = self.make_dict([('key', 'value1'), ('key2', 'value2')])
-        self.assertEqual({'key', 'key3'}, set(d.keys()) ^ {'key2', 'key3'})
+        self.assertEqual({'key', 'key3'}, d.keys() ^ {'key2', 'key3'})
 
     def test_isdisjoint(self):
         d = self.make_dict([('key', 'value1')])