diff --git a/narwhals/_utils.py b/narwhals/_utils.py
index 370091a461..a02552e90a 100644
--- a/narwhals/_utils.py
+++ b/narwhals/_utils.py
@@ -1314,7 +1314,11 @@ def is_slice_index(obj: Any) -> TypeIs[_SliceIndex]:
     return isinstance(obj, slice) and (
         isinstance(obj.start, int)
         or isinstance(obj.stop, int)
-        or (isinstance(obj.step, int) and obj.start is None and obj.stop is None)
+        or (
+            isinstance(obj.step, (int, NoneType))
+            and obj.start is None
+            and obj.stop is None
+        )
     )
 
 
@@ -2141,3 +2145,6 @@ def __repr__(self) -> str:  # pragma: no cover
 # the "no_default" sentinel should typically be used when one of the valid parameter
 # values is None, as otherwise we cannot determine if the caller has set that value.
 no_default = _NoDefault.no_default
+
+# Can be imported from types in Python 3.10
+NoneType = type(None)
diff --git a/tests/series_only/getitem_test.py b/tests/series_only/getitem_test.py
index cecb8099ee..aa63ac8414 100644
--- a/tests/series_only/getitem_test.py
+++ b/tests/series_only/getitem_test.py
@@ -5,7 +5,7 @@
 import pytest
 
 import narwhals as nw
-from tests.utils import assert_equal_data
+from tests.utils import assert_equal_data, assert_equal_series
 
 if TYPE_CHECKING:
     from tests.utils import ConstructorEager
@@ -38,6 +38,9 @@ def test_by_slice(constructor_eager: ConstructorEager) -> None:
     result = {"b": df[[], 1]}
     expected = {"b": []}
     assert_equal_data(result, expected)
+    result_ser = df[:, 0][slice(None)]
+    expected_ser = [1, 2, 3]
+    assert_equal_series(result_ser, expected_ser, name="a")
 
 
 def test_getitem_arrow_scalar() -> None: