diff --git a/docs/index.rst b/docs/index.rst
index 2173f4e..42e04b1 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -48,6 +48,9 @@ A "real-time sync" framework is also (eventually) planned, similar to
 the one developed in the Rattail Project;
 cf. :doc:`rattail-manual:data/sync/index`.
 
+.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
+   :target: https://github.com/psf/black
+
 
 .. toctree::
    :maxdepth: 2