diff --git a/crates/polars-plan/src/dsl/python_udf.rs b/crates/polars-plan/src/dsl/python_udf.rs
index e99ec56f14d5..cd133ceb646e 100644
--- a/crates/polars-plan/src/dsl/python_udf.rs
+++ b/crates/polars-plan/src/dsl/python_udf.rs
@@ -67,7 +67,7 @@ impl PythonUdfExpression {
                 (3, ser_py_version[0], ser_py_version[1] )
             );
         }
-        let buf = &buf[2..];
+        let buf = &buf[3..];
 
         // Load UDF metadata
         let mut reader = Cursor::new(buf);
diff --git a/py-polars/tests/unit/io/cloud/test_cloud.py b/py-polars/tests/unit/io/cloud/test_cloud.py
index a7dcc5c8a8cc..58e341f5b39f 100644
--- a/py-polars/tests/unit/io/cloud/test_cloud.py
+++ b/py-polars/tests/unit/io/cloud/test_cloud.py
@@ -57,9 +57,7 @@ def raises_2() -> pl.CredentialProviderFunctionReturn:
         pl.scan_parquet("s3://bucket/path", credential_provider=raises_2).collect()
 
 
-def test_scan_credential_provider_serialization(
-    monkeypatch: pytest.MonkeyPatch,
-) -> None:
+def test_scan_credential_provider_serialization() -> None:
     err_magic = "err_magic_3"
 
     class ErrCredentialProvider(pl.CredentialProvider):
@@ -74,7 +72,7 @@ def __call__(self) -> pl.CredentialProviderFunctionReturn:
 
     lf = pl.LazyFrame.deserialize(io.BytesIO(serialized))
 
-    with pytest.raises(AssertionError, match=err_magic):
+    with pytest.raises(ComputeError, match=err_magic):
         lf.collect()