diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index aa773af..142b9e1 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -16,7 +16,7 @@ Users are encouraged to use GitHub Discussions for engaging with researchers, de
 
 ### Project Code Style
 
-Code in this repository should conform to PEP8 standards. Style/lint checks are run to validate this. Line length must be limited to no more than 88 characters.
+Code in this repository should conform to PEP8 standards. Style/lint checks are run to validate this. Line length must be limited to no more than 100 characters.
 
 ### Pull Request Checklist
 
diff --git a/prototype_template/template_module/template_class.py b/prototype_template/template_module/template_class.py
index 1cc3132..e047010 100644
--- a/prototype_template/template_module/template_class.py
+++ b/prototype_template/template_module/template_class.py
@@ -8,9 +8,7 @@ class TemplateClass:
 
     def __init__(
         self,
-        some_parameter: Union[
-            int, float, str, bool, List[Union[int, float, str, bool]]
-        ],
+        some_parameter: Union[int, float, str, bool, List[Union[int, float, str, bool]]],
         optional_parameter: Optional[
             Union[int, float, str, bool, List[Union[int, float, str, bool]]]
         ] = None,
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..468dbfa
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,3 @@
+[tool.black]
+line-length = 100
+target-version = ['py37', 'py38', 'py39', 'py310']
diff --git a/tests/README.md b/tests/README.md
index 53bb4a9..ff22713 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -16,7 +16,7 @@ Environments for this repository are configured in [`tox.ini`] as described belo
 
 The `lint` environment ensures that the code meets basic coding standards, including
 
-- [_Black_] formatting style
+- [_Black_] formatting style, as configured by [`pyproject.toml`]
 - [mypy] type annotation checker, as configured by [`mypy.ini`]
 - [pylint], as configured by [`.pylintrc`]
 
@@ -63,6 +63,7 @@ $ tox -ecoverage
 [`mypy.ini`]: /mypy.ini
 [treon]: https://github.com/ReviewNB/treon
 [_Black_]: https://github.com/psf/black
+[`pyproject.toml`]: /pyproject.toml
 [pylint]: https://github.com/PyCQA/pylint
 [`.pylintrc`]: /.pylintrc
 [nbqa]: https://github.com/nbQA-dev/nbQA