diff --git a/_ptcsvp/configure.py b/_ptcsvp/configure.py
index a7185c8..f5021db 100644
--- a/_ptcsvp/configure.py
+++ b/_ptcsvp/configure.py
@@ -6,14 +6,14 @@ from _pytest.config import Config
 from _ptcsvp.plugin import Plugin
 
 
-def pytest_configure(config: Config, plugin_name="csv_params") -> None:
+def pytest_configure(config: Config, plugin_name: str = "csv_params") -> None:
     """
     Register our Plugin
     """
     config.pluginmanager.register(Plugin(config), f"{plugin_name}_plugin")
 
 
-def pytest_unconfigure(config: Config, plugin_name="csv_params") -> None:
+def pytest_unconfigure(config: Config, plugin_name: str = "csv_params") -> None:
     """
     Remove our Plugin
     """
diff --git a/_ptcsvp/parametrize.py b/_ptcsvp/parametrize.py
index 6326d04..2637570 100644
--- a/_ptcsvp/parametrize.py
+++ b/_ptcsvp/parametrize.py
@@ -6,6 +6,7 @@ from pathlib import Path
 from typing import Any, List, Optional, TypedDict
 
 import pytest
+from _pytest.mark import MarkDecorator
 
 from _ptcsvp.plugin import BASE_DIR_KEY, Plugin
 from pytest_csv_params.dialect import CsvParamsDefaultDialect
@@ -14,7 +15,7 @@ from pytest_csv_params.exception import (
     CsvParamsDataFileInvalid,
     CsvParamsDataFileNotFound,
 )
-from pytest_csv_params.types import BaseDir, CsvDialect, DataCastDict, DataFile, IdColName
+from pytest_csv_params.types import BaseDir, CsvDialect, DataCasts, DataFile, IdColName
 
 
 class TestCaseParameters(TypedDict):
@@ -56,9 +57,9 @@ def add_parametrization(
     data_file: DataFile,
     base_dir: BaseDir = None,
     id_col: IdColName = None,
-    data_casts: DataCastDict = None,
+    data_casts: DataCasts = None,
     dialect: CsvDialect = CsvParamsDefaultDialect,
-):
+) -> MarkDecorator:
     """
     Get data from the files and add things to the tests
     """
diff --git a/_ptcsvp/plugin.py b/_ptcsvp/plugin.py
index f01de8b..d872c43 100644
--- a/_ptcsvp/plugin.py
+++ b/_ptcsvp/plugin.py
@@ -2,6 +2,7 @@
 The main Plugin implementation
 """
 
+from _pytest.config import Config
 
 BASE_DIR_KEY = "__pytest_csv_plugins__config__base_dir"
 
@@ -11,7 +12,7 @@ class Plugin:  # pylint: disable=too-few-public-methods
     Plugin Class
     """
 
-    def __init__(self, config) -> None:
+    def __init__(self, config: Config) -> None:
         """
         Hold the pytest config
         """
diff --git a/pytest_csv_params/types.py b/pytest_csv_params/types.py
index e6a5d31..e9f12d7 100644
--- a/pytest_csv_params/types.py
+++ b/pytest_csv_params/types.py
@@ -2,12 +2,11 @@
 Types to ease the usage of the API
 """
 import csv
-from typing import Callable, Dict, Optional, Type, TypeVar
+from typing import Any, Callable, Dict, Optional, Type
 
-T = TypeVar("T")
-
-DataCast = Callable[[str], T]
+DataCast = Callable[[str], Any]
 DataCastDict = Dict[str, DataCast]
+DataCasts = Optional[DataCastDict]
 
 BaseDir = Optional[str]
 IdColName = Optional[str]
diff --git a/tests/test_parametrize.py b/tests/test_parametrize.py
index 8634699..a72adcf 100644
--- a/tests/test_parametrize.py
+++ b/tests/test_parametrize.py
@@ -2,7 +2,7 @@
 Test the Parametrization Feature
 """
 from os.path import dirname, join
-from typing import List, Optional, Tuple
+from typing import List, Optional, Tuple, Type
 
 import pytest
 
@@ -82,7 +82,7 @@ def test_parametrization(  # pylint: disable=too-many-arguments
     id_col: Optional[str],
     result: Optional[Tuple[List[str], List[List[str]]]],
     ids: Optional[List[str]],
-    expect_exception: Optional[Exception],
+    expect_exception: Optional[Type[Exception]],
     expect_message: Optional[str],
 ) -> None:
     """
diff --git a/tests/test_read_csv.py b/tests/test_read_csv.py
index 44b8ddf..dee89e3 100644
--- a/tests/test_read_csv.py
+++ b/tests/test_read_csv.py
@@ -2,7 +2,7 @@
 Test the reading of the CSV
 """
 from os.path import dirname, join
-from typing import Optional
+from typing import Optional, Type
 
 import pytest
 
@@ -35,10 +35,10 @@ from pytest_csv_params.exception import CsvParamsDataFileInvalid, CsvParamsDataF
     ],
 )
 def test_csv_reader(
-    csv_file: Optional[str],
+    csv_file: str,
     base_dir: Optional[str],
     expect_lines: Optional[int],
-    expect_exception: Optional[Exception],
+    expect_exception: Optional[Type[Exception]],
     expect_message: Optional[str],
 ) -> None:
     """