diff --git a/axlearn/common/array_serialization.py b/axlearn/common/array_serialization.py
index 2bd2c40b..1187eba4 100644
--- a/axlearn/common/array_serialization.py
+++ b/axlearn/common/array_serialization.py
@@ -24,6 +24,10 @@
 from axlearn.common.utils import Tensor
 
 
+def _local_size(array: Tensor) -> int:
+    return sum(shard.data.nbytes for shard in array.addressable_shards)
+
+
 def _proxy(fut: asyncio.Future) -> asyncio.Future:
     """Returns a proxy that can be used to await (but does not cancel) `fut`."""
     loop = asyncio.get_event_loop()
@@ -134,7 +138,11 @@ async def async_serialize(
             # Memory usage seems to be proportional to the array size rather than shard sizes.
             # TODO(markblee): Investigate why this is the case.
             _acquire_and_write(
-                t, limiter=limiter, shard=shard, nbytes=array.nbytes, release_tasks=release_tasks
+                t,
+                limiter=limiter,
+                shard=shard,
+                nbytes=_local_size(array),
+                release_tasks=release_tasks,
             )
             for shard in local_shards
         )
@@ -165,7 +173,7 @@ def serialize(
         logging.info("Waiting for previous serialization to finish.")
         self.wait_until_finished()
 
-        max_shard_bytes = max((0, *(array.nbytes for array in arrays)))
+        max_shard_bytes = max((0, *(_local_size(array) for array in arrays)))
         max_concurrent_bytes = self._max_concurrent_bytes
         if max_shard_bytes > max_concurrent_bytes:
             logging.warning(
diff --git a/axlearn/common/array_serialization_test.py b/axlearn/common/array_serialization_test.py
index 3d68516e..09be4adc 100644
--- a/axlearn/common/array_serialization_test.py
+++ b/axlearn/common/array_serialization_test.py
@@ -6,6 +6,7 @@
 import asyncio
 import contextlib
 import functools
+import math
 from typing import List, Optional
 from unittest import mock
 
@@ -315,6 +316,12 @@ async def acquire_and_write(*, shards: List[Shard]):
             max_concurrent_gb=1,
             expect_max_concurrent_gb=1,
         ),
+        # Test non-addressable shards (which are represented by negative numbers).
+        dict(
+            arrays=[[1, 1, -1, -1], [1]],
+            max_concurrent_gb=1,
+            expect_max_concurrent_gb=2,
+        ),
     )
     def test_serialize(
         self, arrays: List[List[int]], max_concurrent_gb: int, expect_max_concurrent_gb: int
@@ -324,8 +331,9 @@ def test_serialize(
                 addressable_shards=[
                     mock.Mock(replica_id=0, **{"data.nbytes": int(shard * 10**9)})
                     for shard in array
+                    if shard >= 0
                 ],
-                nbytes=int(sum(array) * 10**9),
+                nbytes=int(sum(math.fabs(shard) for shard in array) * 10**9),
             )
             for array in arrays
         ]