--- redmine-1.6.1/app/views/admin/plugins.html.erb
+++ redmine/app/views/admin/plugins.html.erb
@@ -25,7 +25,7 @@
     e.preventDefault();
     $.ajax({
       dataType: "jsonp",
-       url: "http://www.redmine.org/plugins/check_updates",
+       url: "//www.redmine.org/plugins/check_updates",
       data: <%= raw_json plugin_data_for_updates(@plugins) %>,
       timeout: 3000,
       beforeSend: function(){