diff --git a/tests/test_engines.py b/tests/test_engines.py
index 65497ca..20a1b04 100644
--- a/tests/test_engines.py
+++ b/tests/test_engines.py
@@ -31,7 +31,7 @@ class EnginesTestCase(unittest.TestCase):
 
     def test_merge_tree_with_sampling(self):
         class TestModel(SampleModel):
-            engine = MergeTree('date', ('date', 'event_id', 'event_group'), sampling_expr='intHash32(event_id)')
+            engine = MergeTree('date', ('date', 'event_id', 'event_group', 'intHash32(event_id)'), sampling_expr='intHash32(event_id)')
         self._create_and_insert(TestModel)
 
     def test_merge_tree_with_granularity(self):