diff --git a/doc/source/index.rst b/doc/source/index.rst
index 49448f2..d6a14d4 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -5,7 +5,7 @@ ACSTOOLS
 ########
 
 Software tools for
-`Advanced Camera for Surveys (ACS) <http://www.stsci.edu/hst/acs/>`_.
+`Advanced Camera for Surveys (ACS) <https://www.stsci.edu/hst/acs/>`_.
 
 Different ways to install the latest release of this package::