diff --git a/docs/extensions.rst b/docs/extensions.rst
index d99f980..1a41bc3 100644
--- a/docs/extensions.rst
+++ b/docs/extensions.rst
@@ -119,6 +119,8 @@ listing of the ones we are aware of:
 
 * `pep8-naming <https://github.com/flintwork/pep8-naming>`_
 
+* `radon <https://github.com/rubik/radon>`_
+
 .. links
 .. _mccabe: https://github.com/flintwork/mccabe
-.. _PyPI: https://pypi.python.org/pypi/
+.. _PyPI: https://pypi.python.org/pypi/
\ No newline at end of file