--- a/course/edit_form.php
+++ b/course/edit_form.php
@@ -94,7 +94,7 @@ class course_edit_form extends moodleform {
             $mform->setConstant('shortname', $course->shortname);
         }
 
-        $mform->addElement('text','idnumber', get_string('idnumbercourse'),'maxlength="100"  size="10"');
+        $mform->addElement('text','idnumber', get_string('idnumbercourse'),'maxlength="100"  size="20"');
         $mform->addHelpButton('idnumber', 'idnumbercourse');
         $mform->setType('idnumber', PARAM_RAW);
         if (!empty($course->id) and !has_capability('moodle/course:changeidnumber', $coursecontext)) {