diff --git a/docs/conf.py b/docs/conf.py
index 175b12f..b33eea9 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -42,7 +42,6 @@
 html_static_path = ["_static"]
 
 html_theme = "sphinx_rtd_theme"
-html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
 
 nitpicky = True
 nitpick_ignore_regex = [
diff --git a/pyproject.toml b/pyproject.toml
index 9aafb9d..8be6b2d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -16,6 +16,7 @@ classifiers = [
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
 ]
 dynamic = [
   "version",
@@ -38,7 +39,6 @@ optional-dependencies.lint = [
   "isort",
   "mypy",
   "pyproject-fmt",
-  "safety",
   "tox-ini-fmt",
 ]
 optional-dependencies.test = [
diff --git a/src/enlyze/schema.py b/src/enlyze/schema.py
index ebd31a9..7c49e04 100644
--- a/src/enlyze/schema.py
+++ b/src/enlyze/schema.py
@@ -1,17 +1,18 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:  # pragma: no cover
+    from _typeshed import DataclassInstance
 import typing
 from dataclasses import is_dataclass
 from types import UnionType
-from typing import Any, Protocol
 
 import pandas
 
 
-class DataclassTypeOrInstance(Protocol):
-    __dataclass_fields__: dict[str, Any]
-
-
 def _flat_dataclass_schema(
-    dataclass_obj_or_type: DataclassTypeOrInstance,
+    dataclass_obj_or_type: DataclassInstance | type[DataclassInstance],
     path_separator: str,
     _parent_path: list[str] = [],
 ) -> list[str]:
@@ -42,7 +43,7 @@ def _flat_dataclass_schema(
 
 def dataframe_ensure_schema(
     df: pandas.DataFrame,
-    dataclass_obj_or_type: DataclassTypeOrInstance,
+    dataclass_obj_or_type: DataclassInstance | type[DataclassInstance],
     path_separator: str = ".",
 ) -> pandas.DataFrame:
     """Add missing columns to ``df`` based on flattened dataclass schema"""