diff --git a/axlearn/common/input_grain.py b/axlearn/common/input_grain.py
index ed52f33b..e06d8ae3 100644
--- a/axlearn/common/input_grain.py
+++ b/axlearn/common/input_grain.py
@@ -40,7 +40,6 @@
 from absl import logging
 from array_record.python.array_record_data_source import PathLikeOrFileInstruction
 from grain._src.python.data_loader import _determine_worker_count
-from grain._src.python.dataset import stats as dataset_stats
 from grain._src.python.dataset.transformations import packing
 from grain._src.python.dataset.transformations import slice as slice_dataset
 from jax.experimental import multihost_utils
@@ -181,8 +180,7 @@ class _UnbatchDatasetIterator(grain.DatasetIterator):
     """An iterator that unbatches np.arrays along dim=0."""
 
     def __init__(self, parent: grain.DatasetIterator):
-        super().__init__(stats=None)
-        self._parent = parent
+        super().__init__(parent)
         # Index within the unbatched inputs.
         self._index = 0
         self._current_batch = None
@@ -467,10 +465,8 @@ def __init__(
         *,
         pad_example: Any,
         length: int,
-        stats: dataset_stats.Stats,
     ):
-        super().__init__(stats)
-        self._parent = parent
+        super().__init__(parent)
         self._pad_example = pad_example
         self._length = length
         self._i = 0
@@ -516,7 +512,6 @@ def __iter__(self):
             parent_iter,
             pad_example=self._pad_example,
             length=self._length,
-            stats=self._stats,
         )
 
 
diff --git a/axlearn/common/input_grain_lm.py b/axlearn/common/input_grain_lm.py
index 68b36463..d408cfc1 100644
--- a/axlearn/common/input_grain_lm.py
+++ b/axlearn/common/input_grain_lm.py
@@ -3,10 +3,12 @@
 """Input processing for language modeling using Grain."""
 
 import functools
+import logging
 import sys
 from typing import Optional, Protocol
 
 import numpy as np
+from grain._src.python.dataset.transformations.prefetch import MultiprocessPrefetchIterDataset
 
 from axlearn.common import input_grain, input_grain_text
 from axlearn.common.config import ConfigOr, maybe_instantiate
@@ -124,8 +126,11 @@ def text_to_lm_training_input(
     split_fn = functools.partial(
         _trim_or_pad_and_batch, max_padding_fraction=max_padding_fraction, pad_id=vocab.pad_id
     )
-    # Only repeat if not already infinite.
-    if len(ds) != sys.maxsize:
+    if isinstance(ds, MultiprocessPrefetchIterDataset):
+        # Dataset types like MultiprocessPrefetchIterDataset have no len() or repeat() function
+        logging.info("Skipping repeat for ds: %s`", ds)
+    elif len(ds) != sys.maxsize:
+        # Only repeat if not already infinite.
         ds = ds.repeat(num_epochs=None)
     ds = input_grain_text.tokenize(ds, vocab={"text": vocab}, with_eos=True)
     ds = input_grain.rekey(ds, key_map={"target_labels": "text"})
diff --git a/axlearn/common/input_grain_lm_test.py b/axlearn/common/input_grain_lm_test.py
index deb1d189..5ca0704e 100644
--- a/axlearn/common/input_grain_lm_test.py
+++ b/axlearn/common/input_grain_lm_test.py
@@ -201,6 +201,31 @@ def test_training_lm_processor_infinite_dataset(self):
             max_padding_fraction=0.0,
         )
 
+    @pytest.mark.skipif(
+        not os.path.exists(t5_sentence_piece_vocab_file), reason="Missing testdata."
+    )
+    def test_training_lm_processor_dataset_no_len_func(self):
+        max_len = 32
+        vocab = seqio.SentencePieceVocabulary(
+            sentencepiece_model_file=t5_sentence_piece_vocab_file,
+        )
+        examples = [{"text": f"test_str_#{i}", "index": i} for i in range(10)]
+        ds = prefetch_dataset(
+            maybe_to_iter_dataset(fake_grain_source(examples)),
+            multiprocessing_options=grain.MultiprocessingOptions(
+                num_workers=1,
+                per_worker_buffer_size=1,
+                enable_profiling=False,
+            ),
+        )
+        ds = text_to_lm_training_input(
+            ds,  # check if prefetch dataset breaks the pipeline
+            vocab=vocab,
+            max_len=max_len,
+            window_size=3,
+            max_padding_fraction=0.0,
+        )
+
     @parameterized.parameters(
         dict(
             expected_batches=[
diff --git a/axlearn/common/input_grain_test.py b/axlearn/common/input_grain_test.py
index 7bf1f866..4cfed0e7 100644
--- a/axlearn/common/input_grain_test.py
+++ b/axlearn/common/input_grain_test.py
@@ -258,7 +258,7 @@ def convert_examples(x, rng: np.random.Generator):
 
         ds = range_dataset(start=1, stop=10)
         ds = ds.repeat(None).batch(3)
-        ds = ds.map(convert_examples, seed=123)
+        ds = ds.random_map(convert_examples, seed=123)
         ds = unbatch(maybe_to_iter_dataset(ds))
         ds = iter(ds)
         self._test_checkpointing(ds)
diff --git a/pyproject.toml b/pyproject.toml
index 92414e36..7fb7bd4e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -150,7 +150,7 @@ orbax = [
 ]
 # Grain input processing. Currently does not support macos.
 grain = [
-    "grain==0.2.1; platform_machine == 'x86_64'",
+    "grain==0.2.3; platform_machine == 'x86_64'",
 ]
 # Audio dependencies.
 audio = [