diff --git a/python/src/iceberg/transforms.py b/python/src/iceberg/transforms.py
index 7945210ec0b2..3ebc19219bb9 100644
--- a/python/src/iceberg/transforms.py
+++ b/python/src/iceberg/transforms.py
@@ -64,10 +64,10 @@ def __repr__(self):
     def __str__(self):
         return self._transform_string
 
-    def __call__(self, value: S) -> Optional[T]:
+    def __call__(self, value: Optional[S]) -> Optional[T]:
         return self.apply(value)
 
-    def apply(self, value: S) -> Optional[T]:
+    def apply(self, value: Optional[S]) -> Optional[T]:
         ...
 
     def can_transform(self, source: IcebergType) -> bool:
@@ -83,10 +83,8 @@ def preserves_order(self) -> bool:
     def satisfies_order_of(self, other) -> bool:
         return self == other
 
-    def to_human_string(self, value) -> str:
-        if value is None:
-            return "null"
-        return str(value)
+    def to_human_string(self, value: Optional[S]) -> str:
+        return str(value) if value is not None else "null"
 
     @property
     def dedup_name(self) -> str:
@@ -119,11 +117,8 @@ def num_buckets(self) -> int:
     def hash(self, value: S) -> int:
         raise NotImplementedError()
 
-    def apply(self, value: S) -> Optional[int]:
-        if value is None:
-            return None
-
-        return (self.hash(value) & IntegerType.max) % self._num_buckets
+    def apply(self, value: Optional[S]) -> Optional[int]:
+        return (self.hash(value) & IntegerType.max) % self._num_buckets if value else None
 
     def result_type(self, source: IcebergType) -> IcebergType:
         return IntegerType()
diff --git a/python/tox.ini b/python/tox.ini
index 92757798b6ac..8be70e957c48 100644
--- a/python/tox.ini
+++ b/python/tox.ini
@@ -69,7 +69,7 @@ commands =
 deps =
     mypy
 commands =
-    mypy --no-implicit-optional --install-types --non-interactive --config tox.ini src
+    mypy --install-types --non-interactive --config tox.ini src
 
 [testenv:docs]
 basepython = python3
@@ -97,5 +97,11 @@ python =
   3.8: py38, linters
   3.9: py39
 
+[mypy]
+
+no_implicit_optional=True
+warn_redundant_casts=True
+warn_unreachable=True
+
 [mypy-pyarrow.*]
 ignore_missing_imports = True