diff --git a/README.md b/README.md
index 5f599c9..24fb4e2 100644
--- a/README.md
+++ b/README.md
@@ -7,6 +7,12 @@ Source code for https://gaussian.dev
 
 See [LICENSE](LICENSE) for details.
 
+## Theme
+
+The base hugo-bearblog theme was obtained from
+https://github.com/janraasch/hugo-bearblog. It is
+vendored as a subtree, and can be updated using the `git subtree` commands.
+
 ## Questions/Comments/Contributing
 
 At the time of writing, this project is hosted on a Forgejo instance at