diff --git a/xrft/padding.py b/xrft/padding.py
index acb8c45..cb8ccbd 100644
--- a/xrft/padding.py
+++ b/xrft/padding.py
@@ -1,6 +1,7 @@
 """
 Functions to pad and unpad a N-dimensional regular grid
 """
+
 import numpy as np
 from xarray.core.utils import either_dict_or_kwargs
 
@@ -311,7 +312,9 @@ def _pad_coordinates_callback(vector, iaxis_pad_width, iaxis, kwargs):
     vector[:n_start] = (
         vmin - n_start * spacing + np.linspace(0, spacing * (n_start - 1), n_start)
     )
-    vector[-n_end:] = vmax + spacing + np.linspace(0, spacing * (n_end - 1), n_end)
+    vector[len(vector) - n_end :] = (
+        vmax + spacing + np.linspace(0, spacing * (n_end - 1), n_end)
+    )
     return vector
 
 
@@ -438,6 +441,6 @@ def _pad_width_to_slice(pad_width, size):
         A slice object for removing the padded elements of the coordinate
         array.
     """
-    if type(pad_width) == int:
+    if isinstance(pad_width, int):
         pad_width = (pad_width, pad_width)
     return slice(pad_width[0], size - pad_width[1])
diff --git a/xrft/tests/test_padding.py b/xrft/tests/test_padding.py
index c4eb391..2747f8b 100644
--- a/xrft/tests/test_padding.py
+++ b/xrft/tests/test_padding.py
@@ -1,6 +1,7 @@
 """
 Unit tests for padding functions
 """
+
 import pytest
 import numpy as np
 import xarray as xr
@@ -208,11 +209,14 @@ def test_unpad_pop_pad_width_attributes(sample_da_2d, pad_width_arg):
     (
         {"x": 4, "y": 3},
         {"x": 4},
+        {"x": 0},
         {"y": 3},
+        {"x": 4, "y": 0},
         {"x": (4, 3), "y": 3},
         {"x": (4, 3), "y": (5, 3)},
         {"x": (4, 3)},
         {"y": (5, 3)},
+        {"x": (0, 3), "y": (5, 0)},
     ),
 )
 def test_unpad_ifft_fft_pad_round_trip(sample_da_2d, pad_width):