diff --git a/test/test_loopy.py b/test/test_loopy.py
index c83db5d56948e952eb0e59f46e55c287e7d5bc01..9eaece6a83ae86de4af0eeaf4356f6502024ee40 100644
--- a/test/test_loopy.py
+++ b/test/test_loopy.py
@@ -1344,7 +1344,7 @@ def test_missing_definition_check_respects_aliases():
                         dtype=np.float64, shape=("n",), base_storage="base")
          },
          target=lp.CTarget(),
-         silenced_warnings=frozenset({"read_no_write(b)"}))
+         silenced_warnings=frozenset(["read_no_write(b)"]))
 
     lp.generate_code_v2(knl)