diff --git a/enrol/guest/db/install.php b/enrol/guest/db/install.php
new file mode 100644
index 0000000000000..c5e8c68d8f462
--- /dev/null
+++ b/enrol/guest/db/install.php
@@ -0,0 +1,35 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Guest enrol plugin installation.
+ *
+ * @package    enrol
+ * @subpackage guest
+ * @copyright  2011 Petr Skoda  {@link http://skodak.org}
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+function xmldb_enrol_guest_install() {
+    global $CFG, $DB;
+
+    // migrate settings during 2.0 upgrade
+
+    // convert all null passwords to empty strings
+    $DB->set_field('enrol', 'password', '', array('enrol'=>'guest', 'password'=>null));
+}
diff --git a/enrol/guest/db/upgrade.php b/enrol/guest/db/upgrade.php
new file mode 100644
index 0000000000000..d04b36ee5d1c7
--- /dev/null
+++ b/enrol/guest/db/upgrade.php
@@ -0,0 +1,43 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * This file keeps track of upgrades to the guest enrolment plugin
+ *
+ * @package    enrol
+ * @subpackage guest
+ * @copyright  2011 Petr Skoda {@link http://skodak.org
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+function xmldb_enrol_guest_upgrade($oldversion) {
+    global $CFG, $DB, $OUTPUT;
+
+    $dbman = $DB->get_manager();
+
+    if ($oldversion < 2011112901) {
+        // convert all null passwords to empty strings
+        $DB->set_field('enrol', 'password', '', array('enrol'=>'guest', 'password'=>null));
+
+        upgrade_plugin_savepoint(true, 2011112901, 'enrol', 'guest');
+    }
+
+    return true;
+}
+
+
diff --git a/enrol/guest/lib.php b/enrol/guest/lib.php
index ac4a5cf8963e2..da1d2f168007c 100644
--- a/enrol/guest/lib.php
+++ b/enrol/guest/lib.php
@@ -327,6 +327,22 @@ public function course_updated($inserted, $course, $data) {
         }
     }
 
+    /**
+     * Add new instance of enrol plugin.
+     * @param object $course
+     * @param array instance fields
+     * @return int id of new instance, null if can not be created
+     */
+    public function add_instance($course, array $fields = NULL) {
+        $fields = (array)$fields;
+
+        if (!isset($fields['password'])) {
+            $fields['password'] = '';
+        }
+
+        return parent::add_instance($course, $fields);
+    }
+
     /**
      * Add new instance of enrol plugin with default settings.
      * @param object $course
diff --git a/enrol/guest/version.php b/enrol/guest/version.php
index 0f235c6a0d6e0..125592f212b51 100644
--- a/enrol/guest/version.php
+++ b/enrol/guest/version.php
@@ -25,6 +25,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2011112900;        // The current plugin version (Date: YYYYMMDDXX)
+$plugin->version   = 2011112901;        // The current plugin version (Date: YYYYMMDDXX)
 $plugin->requires  = 2011112900;        // Requires this Moodle version
 $plugin->component = 'enrol_guest';     // Full name of the plugin (used for diagnostics)