--- a/opac-tmpl/bootstrap/js/openlibrary.js	
+++ a/opac-tmpl/bootstrap/js/openlibrary.js	
@@ -26,7 +26,7 @@ KOHA.OpenLibrary = {
         var scriptElement = document.createElement("script");
         scriptElement.setAttribute("id", "jsonScript");
         scriptElement.setAttribute("src",
-            "http://openlibrary.org/api/books?bibkeys=" + escape(bibkeys) +
+            "https://openlibrary.org/api/books?bibkeys=" + escape(bibkeys) +
             "&callback=KOHA.OpenLibrary.olCallBack&jscmd=data");
         scriptElement.setAttribute("type", "text/javascript");
         document.documentElement.firstChild.appendChild(scriptElement);