diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 3a09e079dd9855fce90124ab9a52a600904ffe44..64c072dabb67fcba5e673e771662f88135c4f8f6 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -49,7 +49,7 @@ To set up `apex` for local development:
 
    Now you can make your changes locally.
 
-4. When you're done making changes, run all the checks, doc builder and spell checker with `tox <http://tox.readthedocs.org/en/latest/install.html>`_ one command::
+4. When you're done making changes, run all the checks, doc builder and spell checker with `tox <http://tox.readthedocs.io/en/latest/install.html>`_ one command::
 
     tox