Capital S is the canonical URL
diff --git a/docs/contributing.rst b/docs/contributing.rst
index 4bb1461..3de41fd 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -287,5 +287,5 @@
 .. _`tox`: https://pypi.python.org/pypi/tox
 .. _`virtualenv`: https://pypi.python.org/pypi/virtualenv
 .. _`pip`: https://pypi.python.org/pypi/pip
-.. _`sphinx`: https://pypi.python.org/pypi/sphinx
+.. _`sphinx`: https://pypi.python.org/pypi/Sphinx
 .. _`reStructured Text`: http://sphinx-doc.org/rest.html