diff --git a/swiftgalaxy/reader.py b/swiftgalaxy/reader.py
index a294c9a..f1b6327 100644
--- a/swiftgalaxy/reader.py
+++ b/swiftgalaxy/reader.py
@@ -17,7 +17,7 @@
 the :class:`SWIFTGalaxy` class.
 """
 
-from warnings import warn, catch_warnings, filterwarnings
+from warnings import warn
 from copy import deepcopy
 import numpy as np
 from scipy.spatial.transform import Rotation
@@ -57,16 +57,7 @@ def _apply_box_wrap(coords: cosmo_array, boxsize: Optional[cosmo_array]) -> cosm
     """
     if boxsize is None:
         return coords
-    # Would like to ensure comoving coordinates here, but metadata gives boxsize as a
-    # unyt_array instead of a cosmo_array. Pending swiftsimio issue #128. When
-    # implementing, remove cast(s) to cosmo_array in test_coordinate_transformations.
-    with catch_warnings():
-        filterwarnings(
-            "ignore", category=RuntimeWarning, message="Mixing ufunc arguments"
-        )
-        retval = (coords + boxsize / 2.0) % boxsize - boxsize / 2.0
-    retval.comoving = coords.comoving
-    retval.cosmo_factor = coords.cosmo_factor
+    retval = (coords + boxsize / 2.0) % boxsize - boxsize / 2.0
     return retval
 
 
diff --git a/tests/test_coordinate_transformations.py b/tests/test_coordinate_transformations.py
index 4dc5615..e6817ac 100644
--- a/tests/test_coordinate_transformations.py
+++ b/tests/test_coordinate_transformations.py
@@ -1,7 +1,6 @@
 import pytest
 import numpy as np
 import unyt as u
-from warnings import warn
 from unyt.testing import assert_allclose_units
 from swiftsimio.objects import cosmo_array, cosmo_factor, a
 from scipy.spatial.transform import Rotation
@@ -378,21 +377,8 @@ def test_box_wrap(self, sg, particle_name, coordinate_name):
         """
         Check that translating by two box lengths wraps back to previous state.
         """
-        if hasattr(sg.metadata.boxsize, "comoving"):
-            # if this warning produced, remove cast to cosmo_array below
-            # and this warning block
-            warn(
-                "SWIFTSimIO is now giving boxsize as comso_array, update this test.",
-                category=RuntimeWarning,
-            )
-        else:
-            boxsize = cosmo_array(
-                sg.metadata.boxsize,
-                comoving=True,
-                cosmo_factor=cosmo_factor(a**1, scale_factor=1.0),
-            )
         xyz_before = getattr(getattr(sg, particle_name), f"{coordinate_name}")
-        sg.translate(-2 * boxsize)  # -2x box size
+        sg.translate(-2 * sg.metadata.boxsize)  # -2x box size
         xyz = getattr(getattr(sg, particle_name), f"{coordinate_name}")
         assert_allclose_units(xyz_before, xyz, rtol=1.0e-4, atol=abstol_c)
 
@@ -544,14 +530,3 @@ def test_copied_velocity_transform(self, sg):
         assert_allclose_units(
             sg.gas.velocities, sg2.gas.velocities, rtol=1.0e-4, atol=abstol_v
         )
-
-
-@pytest.mark.xfail
-class TestBoxsizeIsCosmoArray:
-    def test_boxsize_is_cosmo_array(self, sg):
-        # When swiftsimio issue #128 is resolved:
-        #   - This test will unexpectedly pass.
-        #   - Remove this test.
-        #   - Remove catch_warnings and filterwarnings from _apply_box_wrap in reader.py
-        #   - Remove explicit attribute copying in _apply_box_wrap in reader.py
-        assert hasattr(sg.metadata.boxsize, "comoving")