diff --git a/themes/bootstrap3/js/preview.js b/themes/bootstrap3/js/preview.js
index 718f92d03a12af9247021fc524e6c58da16b1bcd..513ec2667a818ab09028cffd696343fabd0cabd2 100644
--- a/themes/bootstrap3/js/preview.js
+++ b/themes/bootstrap3/js/preview.js
@@ -25,7 +25,7 @@ function getHTPreviews(skeys) {
     for(var i = 0; i < bibkeys.length; i++) {
         batch.push(bibkeys[i]);
         if ((i > 0 && i % 20 == 0) || i == bibkeys.length-1) {
-            var script = 'http://catalog.hathitrust.org/api/volumes/brief/json/'
+            var script = 'https://catalog.hathitrust.org/api/volumes/brief/json/'
                 + batch.join('|') + '&callback=processHTBookInfo';
             $.getScript(script);
             batch = [];