diff --git a/tests/test_key_handling/test_key_derivation/test_tree.py b/tests/test_key_handling/test_key_derivation/test_tree.py
index 8bd6491..d6e735d 100644
--- a/tests/test_key_handling/test_key_derivation/test_tree.py
+++ b/tests/test_key_handling/test_key_derivation/test_tree.py
@@ -28,13 +28,13 @@ def test_hkdf_mod_r(test) -> None:
 
 @pytest.mark.parametrize(
     'seed',
-    [b'\x00'*32]
+    [b'\x00' * 32]
 )
 @pytest.mark.parametrize(
     'key_info',
-    [b'\x00'*32, b'\x01\x23\x45\x67\x89\xAB\xBC\xDE\xFF', b'\xFF'*16]
+    [b'\x00' * 32, b'\x01\x23\x45\x67\x89\xAB\xBC\xDE\xFF', b'\xFF' * 16]
 )
-def test_hkdf_mod_r_key_info(seed: bytes, key_info:bytes) -> None:
+def test_hkdf_mod_r_key_info(seed: bytes, key_info: bytes) -> None:
     assert bls.KeyGen(seed, key_info) == _HKDF_mod_r(IKM=seed, key_info=key_info)