diff --git a/tests/datasets/test_sampler.py b/tests/datasets/test_sampler.py
index 7614c7dd8..cfe2c5eaf 100644
--- a/tests/datasets/test_sampler.py
+++ b/tests/datasets/test_sampler.py
@@ -246,7 +246,10 @@ def test_deterministic_sampler_constant_memory():
     sampler = deterministic_sampler([0], [num_frames], shuffle=True, seed=0)
     assert len(sampler) == num_frames
     sampler.load_state_dict({"epoch": 3, "start_index": num_frames - 3})
-    tail = list(sampler)
+    # Collect via the iterator: list(sampler) would call PyObject_LengthHint -> sampler.__len__
+    # (the full epoch length, here 10**12) and pre-allocate that many slots before iterating. The
+    # iterator itself exposes no length hint, so this stays O(1) like the resumed epoch it drains.
+    tail = list(iter(sampler))
     assert len(tail) == 3
     assert all(0 <= idx < num_frames for idx in tail)