diff --git a/docs/config/dependency.md b/docs/config/dependency.md
index 79dd796b1..0a9c1fa9c 100644
--- a/docs/config/dependency.md
+++ b/docs/config/dependency.md
@@ -147,6 +147,25 @@ foo[cli,crypto]==1.*
 
 Note that the features come immediately after the package name, before any [version specifiers](#version-specifiers).
 
+One feature group can extend another feature group by using "self-dependency". For example, for a project called `awesome_project`, the `dev` feature group in the following `pyproject.toml` file would select everything in the `crypto` feature group, plus `black`:
+
+=== ":octicons-file-code-16: pyproject.toml"
+
+    ```toml
+    [project]
+    name = "awesome-project"
+    
+    [project.optional-dependencies]
+    crypto = [
+      "PyJWT",
+      "cryptography",
+    ]
+    dev = [
+      "awesome-project[crypto]",
+      "black",
+    ]
+    ```
+
 ## Direct references
 
 Instead of using normal [version specifiers](#version-specifiers) and fetching packages from an index like PyPI, you can define exact sources using [direct references](https://peps.python.org/pep-0440/#direct-references) with an explicit [URI](https://en.wikipedia.org/wiki/Uniform_Resource_Identifier#Syntax).