diff --git a/docs/development/c-bindings.rst b/docs/development/c-bindings.rst
index 10d5fc1..993a4ab 100644
--- a/docs/development/c-bindings.rst
+++ b/docs/development/c-bindings.rst
@@ -3,7 +3,7 @@
 
 C bindings are bindings to C libraries, using cffi_ whenever possible.
 
-.. _cffi: http://cffi.readthedocs.org
+.. _cffi: https://cffi.readthedocs.org
 
 Bindings live in :py:mod:`cryptography.hazmat.bindings`.