diff --git a/altair/utils/data.py b/altair/utils/data.py
index 8ab46a6f7..61923231c 100644
--- a/altair/utils/data.py
+++ b/altair/utils/data.py
@@ -14,7 +14,6 @@
     TypeVar,
     Union,
     Dict,
-    Optional,
     overload,
     runtime_checkable,
 )
@@ -54,7 +53,7 @@ class SupportsGeoInterface(Protocol):
     str, Union[str, Dict[Any, Any], List[Dict[Any, Any]]]
 ]
 ToValuesReturnType: TypeAlias = Dict[str, Union[Dict[Any, Any], List[Dict[Any, Any]]]]
-SampleReturnType = Optional[Union[pd.DataFrame, Dict[str, Sequence], "pa.lib.Table"]]
+SampleReturnType = Union[pd.DataFrame, Dict[str, Sequence], "pa.lib.Table", None]
 
 
 def is_data_type(obj: Any) -> TypeIs[DataType]:
diff --git a/pyproject.toml b/pyproject.toml
index d96a5d4b1..563b8e1d1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -320,6 +320,10 @@ unfixable= [
 [tool.ruff.lint.mccabe]
 max-complexity = 18
 
+[tool.ruff.lint.flake8-tidy-imports.banned-api]
+# https://docs.astral.sh/ruff/settings/#lint_flake8-tidy-imports_banned-api
+"typing.Optional".msg = "Use `Union[T, None]` instead.\n`typing.Optional` is likely to be confused with `altair.Optional`, which have a similar but different semantic meaning.\nSee https://github.com/vega/altair/pull/3449"
+
 [tool.ruff.format]
 quote-style = "double"
 indent-style = "space"