diff --git a/python_otbr_api/__init__.py b/python_otbr_api/__init__.py
index 36765d4..e20b623 100644
--- a/python_otbr_api/__init__.py
+++ b/python_otbr_api/__init__.py
@@ -5,7 +5,7 @@
 import json
 
 import aiohttp
-import voluptuous as vol  # type:ignore[import]
+import voluptuous as vol  # type: ignore[import]
 
 from .models import ActiveDataSet, PendingDataSet, Timestamp
 
diff --git a/python_otbr_api/models.py b/python_otbr_api/models.py
index 952c080..dcf0ee7 100644
--- a/python_otbr_api/models.py
+++ b/python_otbr_api/models.py
@@ -5,7 +5,7 @@
 from dataclasses import dataclass
 from typing import Any
 
-import voluptuous as vol  # type:ignore[import]
+import voluptuous as vol  # type: ignore[import]
 
 
 @dataclass
diff --git a/requirements-test.txt b/requirements-test.txt
index 8d51e7e..45952a8 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,4 +1,4 @@
-black==25.12.0
+black==26.1.0
 flake8==7.3.0
 mypy==1.19.1
 pylint==4.0.4
diff --git a/tests/test_util/aiohttp.py b/tests/test_util/aiohttp.py
index 5adcf91..2eb2e57 100644
--- a/tests/test_util/aiohttp.py
+++ b/tests/test_util/aiohttp.py
@@ -14,7 +14,6 @@
 from multidict import CIMultiDict
 from yarl import URL
 
-
 RETYPE = type(re.compile(""))
 
 # pylint: disable=unused-argument, too-many-arguments, too-many-instance-attributes