diff --git a/lib/formslib.php b/lib/formslib.php
index 2af556d..2cce08e 100644
--- a/lib/formslib.php
+++ b/lib/formslib.php
@@ -582,6 +582,9 @@ class moodleform {
             foreach ($elementobjs as $elementobj){
                 $elementclone = fullclone($elementobj);
                 $name = $elementclone->getName();
+                if ('checkbox' == $elementclone->_type) {
+                    unset($elementclone->_attributes['id']);
+                }
                 $namecloned[] = $name;
                 if (!empty($name)) {
                     $elementclone->setName($name."[$i]");