diff --git a/tests/test_post_naming.py b/tests/test_post_naming.py
index ff2f662..3bc241b 100644
--- a/tests/test_post_naming.py
+++ b/tests/test_post_naming.py
@@ -294,7 +294,7 @@ def test_a_name_reused_across_many_posts_is_still_caught():
     """The other half of the same property — the cap has to keep working once
     the unit changes. Measured habits: tamadaheijun's `comic2` spans 8 posts,
     conto's `seth2` 5."""
-    counts = token_frequencies([["comic2_%02d.jpg" % i] for i in range(8)])
+    counts = token_frequencies([[f"comic2_{i:02d}.jpg"] for i in range(8)])
 
     assert counts["comic2"] == 8
     assert shared_identity({"comic2"}, {"comic2"}, counts) == (0.0, None)