diff --git a/mistral/tests/unit/engine/test_dataflow.py b/mistral/tests/unit/engine/test_dataflow.py
index e9feba762..da99ffcf8 100644
--- a/mistral/tests/unit/engine/test_dataflow.py
+++ b/mistral/tests/unit/engine/test_dataflow.py
@@ -1402,7 +1402,7 @@ class DataFlowTest(test_base.BaseTest):
         res = expr.evaluate('<% $.keys() %>', ctx)
 
         self.assertIsNotNone(res)
-        self.assertIsInstance(res, list)
+        self.assertIsInstance(res, set)
         self.assertEqual(2, len(res))
         self.assertIn('k1', res)
         self.assertIn('k2', res)