diff --git a/trx/tests/test_memmap.py b/trx/tests/test_memmap.py
index 21451a4..1436a1b 100644
--- a/trx/tests/test_memmap.py
+++ b/trx/tests/test_memmap.py
@@ -523,10 +523,12 @@ def test_load_zip_with_local_header_extra_field():
             local_info = []
             extra = b"\x00\x00\x04\x00TEST"  # 8-byte extra field
 
+            # TRX stores arrays little-endian on disk; serialize the fixture
+            # explicitly so it is valid on big-endian hosts too (issue #113).
             for name, data in [
                 ("header.json", json.dumps(header).encode()),
-                ("positions.3.float32", positions.tobytes()),
-                ("offsets.uint64", offsets.tobytes()),
+                ("positions.3.float32", positions.astype("<f4").tobytes()),
+                ("offsets.uint64", offsets.astype("<u8").tobytes()),
             ]:
                 offset = f.tell()
                 fname = name.encode()