diff --git a/tests/test_mutators.py b/tests/test_mutators.py
index 418e19e5268..1f92b23dc40 100644
--- a/tests/test_mutators.py
+++ b/tests/test_mutators.py
@@ -163,11 +163,11 @@ def test_flatten(self):
         # check there was a mutation
         assert ex1['text'] == "\n".join(e['text'] for e in [EXAMPLE1])
         assert ex2['text'] == "\n".join(
-            h for h in [EXAMPLE1['text'], EXAMPLE1['labels'][0], EXAMPLE2['text']]
+            [EXAMPLE1['text'], EXAMPLE1['labels'][0], EXAMPLE2['text']]
         )
         assert ex3['text'] == "\n".join(e['text'] for e in [EXAMPLE3])
         assert ex4['text'] == "\n".join(
-            h for h in [EXAMPLE3['text'], EXAMPLE3['labels'][0], EXAMPLE4['text']]
+            [EXAMPLE3['text'], EXAMPLE3['labels'][0], EXAMPLE4['text']]
         )
 
     def test_last_turn(self):