diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d54f7beee..bf19b18e1 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -15,4 +15,4 @@ to the Sphinx generated docs is provided below.
 
 -->
 
-http://letsencrypt.readthedocs.org/en/latest/contributing.html
+https://letsencrypt.readthedocs.org/en/latest/contributing.html