diff --git a/py-polars/tests/unit/test_scalar.py b/py-polars/tests/unit/test_scalar.py
index 0fdb74cb8843..b00d2a66e043 100644
--- a/py-polars/tests/unit/test_scalar.py
+++ b/py-polars/tests/unit/test_scalar.py
@@ -84,3 +84,21 @@ def test_scalar_identification_function_expr_in_binary() -> None:
 def test_scalar_rechunk_20627() -> None:
     df = pl.concat(2 * [pl.Series([1])]).filter(pl.Series([False, True])).to_frame()
     assert df.rechunk().to_series().n_chunks() == 1
+
+
+def test_split_scalar_21581() -> None:
+    df = pl.DataFrame({"a": [1.0, 2.0, 3.0]})
+    df = df.with_columns(
+        [
+            pl.col("a").shift(-1).alias("next_a"),
+            pl.lit(True).alias("lit"),
+        ]
+    )
+
+    assert df.filter(df["next_a"] != 99.0).with_columns(
+        [pl.lit(False).alias("lit")]
+    ).to_dict(as_series=False) == {
+        "a": [1.0, 2.0],
+        "next_a": [2.0, 3.0],
+        "lit": [False, False],
+    }