diff --git a/icontract/_checkers.py b/icontract/_checkers.py
index 5e18a67..0503317 100644
--- a/icontract/_checkers.py
+++ b/icontract/_checkers.py
@@ -1,4 +1,5 @@
 """Provide functions to add/find contract checkers."""
+
 import contextvars
 import functools
 import inspect
@@ -1289,15 +1290,21 @@ def add_invariant_checks(cls: ClassT) -> None:
 
     for name, prop in names_properties:
         new_prop = property(
-            fget=_decorate_with_invariants(func=prop.fget, is_init=False)
-            if prop.fget
-            else None,
-            fset=_decorate_with_invariants(func=prop.fset, is_init=False)
-            if prop.fset
-            else None,
-            fdel=_decorate_with_invariants(func=prop.fdel, is_init=False)
-            if prop.fdel
-            else None,
+            fget=(
+                _decorate_with_invariants(func=prop.fget, is_init=False)
+                if prop.fget
+                else None
+            ),
+            fset=(
+                _decorate_with_invariants(func=prop.fset, is_init=False)
+                if prop.fset
+                else None
+            ),
+            fdel=(
+                _decorate_with_invariants(func=prop.fdel, is_init=False)
+                if prop.fdel
+                else None
+            ),
             doc=prop.__doc__,
         )
         setattr(cls, name, new_prop)
diff --git a/icontract/_decorators.py b/icontract/_decorators.py
index c7b0ecd..45892ad 100644
--- a/icontract/_decorators.py
+++ b/icontract/_decorators.py
@@ -1,4 +1,5 @@
 """Define public decorators."""
+
 import inspect
 import reprlib
 import traceback
diff --git a/icontract/_metaclass.py b/icontract/_metaclass.py
index a835f03..3be6fea 100644
--- a/icontract/_metaclass.py
+++ b/icontract/_metaclass.py
@@ -1,4 +1,5 @@
 """Define the metaclass necessary to inherit the contracts from the base classes."""
+
 import abc
 import inspect
 import sys
diff --git a/icontract/_represent.py b/icontract/_represent.py
index 2b33fc6..162ca71 100644
--- a/icontract/_represent.py
+++ b/icontract/_represent.py
@@ -1,4 +1,5 @@
 """Handle representations necessary for informative error messages."""
+
 import ast
 import inspect
 import re
@@ -405,7 +406,7 @@ def find_lambda_condition(
 
 
 def inspect_lambda_condition(
-    condition: Callable[..., Any]
+    condition: Callable[..., Any],
 ) -> Optional[ConditionLambdaInspection]:
     """
     Try to extract the source code of the condition as lambda.
diff --git a/icontract/_types.py b/icontract/_types.py
index 727be67..3831967 100644
--- a/icontract/_types.py
+++ b/icontract/_types.py
@@ -1,4 +1,5 @@
 """Define data structures shared among the modules."""
+
 import enum
 import inspect
 import reprlib
diff --git a/setup.py b/setup.py
index a8dd733..d9c48e6 100644
--- a/setup.py
+++ b/setup.py
@@ -4,6 +4,7 @@
 https://packaging.python.org/en/latest/distributing.html
 https://github.com/pypa/sampleproject
 """
+
 import os
 import sys
 
@@ -67,7 +68,7 @@
             "astor==0.8.1",
             "numpy>=1,<2",
             'mypy==1.5.1;python_version>="3.8"',
-            'black==23.9.1;python_version>="3.8"',
+            'black==25.9.0;python_version>="3.8"',
             'deal>=4,<5;python_version>="3.8"',
             'asyncstdlib==3.9.1;python_version>="3.8"',
         ]
diff --git a/tests/mock.py b/tests/mock.py
index ae1cda9..691e4a9 100644
--- a/tests/mock.py
+++ b/tests/mock.py
@@ -1,4 +1,5 @@
 """Provide mock structures used accross the tests."""
+
 from typing import List, Union