diff --git a/.github/workflows/black-lint.yml b/.github/workflows/black-lint.yml
index 317336173..e0b5e1379 100644
--- a/.github/workflows/black-lint.yml
+++ b/.github/workflows/black-lint.yml
@@ -10,4 +10,4 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: psf/black@stable
+      - uses: psf/black@23.12.1
diff --git a/README.md b/README.md
index 5e21ef434..30fc20dc1 100644
--- a/README.md
+++ b/README.md
@@ -91,14 +91,26 @@ https://b3d.interplanety.org/en/using-microsoft-visual-studio-code-as-external-i
 
 #### Formatting
 
-We use [Black](https://black.readthedocs.io/en/stable/index.html).
+We use [Black](https://black.readthedocs.io/en/stable/index.html), version 23.
 
-To make VS Code use it, change the `python.formatting.provider` setting to "black". VS Code will ask you to install Black if not already installed.
+To install it, run `pip install 'black>=23,<24'`.
+
+To make VS Code use it, change the `python.formatting.provider` setting to "black".
 
 To format the whole repo, run `black .` (or `python3 -m black .` depending on how it is installed) from the root of the repo.
 
 The (minimal) configuration for Black is in `/pyproject.toml`.
 
+There is a GitHub action set up to check that PRs and the main branch are formatted: `/.github/workflows/black-lint.yml`
+
+If you see a message such as
+
+```
+Oh no! 💥 💔 💥 The required version `23` does not match the running version `24.1.0`!
+```
+
+Make sure the `black --version` is 23. Install a 23 version with `pip install 'black>=23,<24'`.
+
 #### Updater notes
 
 Be careful if testing the updater when using git, it may mess up the .git folder in some cases.
diff --git a/pyproject.toml b/pyproject.toml
index 2f96472a4..ad3f17c34 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,6 +3,11 @@
 # See https://black.readthedocs.io/en/stable/usage_and_configuration/the_basics.html
 # or `black --help` for what can go here
 
+# Require black version to be 23.x.y
+required-version = '23'
+# Install such a version with:
+# pip install 'black>=23,<24'
+
 line-length = 120
 
 target-version = [