diff --git a/gptc/model.py b/gptc/model.py
index 1f2840d..3b04827 100644
--- a/gptc/model.py
+++ b/gptc/model.py
@@ -81,7 +81,7 @@ class Model:
             for index, category in enumerate(self.names)
         }
 
-    def serialize(self, file: BinaryIO):
+    def serialize(self, file: BinaryIO) -> None:
         file.write(b"GPTC model v5\n")
         file.write(
             json.dumps(
@@ -134,7 +134,7 @@ def deserialize(encoded_model: BinaryIO) -> Model:
 
     weight_code_length = 6 + 2 * len(names)
 
-    weights: Dict[int : List[int]] = {}
+    weights: Dict[int, List[int]] = {}
 
     while True:
         code = encoded_model.read(weight_code_length)
diff --git a/gptc/tokenizer.py b/gptc/tokenizer.py
index 26fa205..337779d 100644
--- a/gptc/tokenizer.py
+++ b/gptc/tokenizer.py
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-from typing import List, Union, Callable
+from typing import List, Union, Callable, Any, cast
 import hashlib
 import emoji
 import unicodedata
@@ -45,13 +45,13 @@ def tokenize(text: str, max_ngram_length: int = 1) -> List[str]:
         return ngrams
 
 
-def _hash_single(token: str, hash_function: Callable) -> int:
+def _hash_single(token: str, hash_function: type) -> int:
     return int.from_bytes(
         hash_function(token.encode("utf-8")).digest()[:6], "big"
     )
 
 
-def _get_hash_function(hash_algorithm: str) -> Callable:
+def _get_hash_function(hash_algorithm: str) -> type:
     if hash_algorithm in {
         "sha224",
         "md5",
@@ -68,12 +68,12 @@ def _get_hash_function(hash_algorithm: str) -> Callable:
         "shake_128",
         "sha3_384",
     }:
-        return getattr(hashlib, hash_algorithm)
+        return cast(type, getattr(hashlib, hash_algorithm))
     else:
         raise ValueError("not a valid hash function: " + hash_algorithm)
 
 
-def hash_single(token: str, hash_algorithm: str) -> List[int]:
+def hash_single(token: str, hash_algorithm: str) -> int:
     return _hash_single(token, _get_hash_function(hash_algorithm))