diff --git a/mod/quiz/category.php b/mod/quiz/category.php
index 94630fa6caf..3198d85fc98 100644
--- a/mod/quiz/category.php
+++ b/mod/quiz/category.php
@@ -99,6 +99,7 @@
                 $cat->info = $form['newinfo'];
                 $cat->publish = $form['newpublish'];
                 $cat->course = $course->id;
+                $cat->stamp = make_unique_id_code();
                 if (!insert_record("quiz_categories", $cat)) {
                     error("Could not insert the new quiz category '$val'");
                 } else {
diff --git a/mod/quiz/db/mysql.php b/mod/quiz/db/mysql.php
index c6719e3cf0b..6729c197803 100644
--- a/mod/quiz/db/mysql.php
+++ b/mod/quiz/db/mysql.php
@@ -147,6 +147,18 @@ function quiz_upgrade($oldversion) {
         }
     }
 
+    if ($oldversion < 2003082700) {
+        table_column("quiz_categories", "", "stamp", "varchar", "255", "", "", "not null");
+        if ($categories = get_records("quiz_categories")) {
+            foreach ($categories as $category) {
+                $stamp = make_unique_id_code();
+                if (!set_field("quiz_categories", "stamp", $stamp, "id", $category->id)) {
+                    notify("Error while adding stamp to category id = $category->id");
+                }
+            }
+        }
+    }
+
     return true;
 }
 
diff --git a/mod/quiz/db/mysql.sql b/mod/quiz/db/mysql.sql
index 9c98f75421b..664bd7a2db3 100644
--- a/mod/quiz/db/mysql.sql
+++ b/mod/quiz/db/mysql.sql
@@ -81,6 +81,7 @@ CREATE TABLE `prefix_quiz_categories` (
   `name` varchar(255) NOT NULL default '',
   `info` text NOT NULL,
   `publish` tinyint(4) NOT NULL default '0',
+  `stamp` varchar(255) NOT NULL default '',
   PRIMARY KEY  (`id`)
 ) TYPE=MyISAM COMMENT='Categories are for grouping questions';
 # --------------------------------------------------------
diff --git a/mod/quiz/db/postgres7.php b/mod/quiz/db/postgres7.php
index 16c16d34f1e..13ca997b411 100644
--- a/mod/quiz/db/postgres7.php
+++ b/mod/quiz/db/postgres7.php
@@ -102,6 +102,18 @@ function quiz_upgrade($oldversion) {
         }
     }
 
+    if ($oldversion < 2003082700) {
+        table_column("quiz_categories", "", "stamp", "varchar", "255", "", "", "not null");
+        if ($categories = get_records("quiz_categories")) {
+            foreach ($categories as $category) {
+                $stamp = make_unique_id_code();
+                if (!set_field("quiz_categories", "stamp", $stamp, "id", $category->id)) {
+                    notify("Error while adding stamp to category id = $category->id");
+                }
+            }
+        }
+    }
+
     return true;
 }
 
diff --git a/mod/quiz/db/postgres7.sql b/mod/quiz/db/postgres7.sql
index 4ecd1afddb9..c8266a59b6f 100644
--- a/mod/quiz/db/postgres7.sql
+++ b/mod/quiz/db/postgres7.sql
@@ -75,6 +75,7 @@ CREATE TABLE prefix_quiz_categories (
   name varchar(255) NOT NULL default '',
   info text NOT NULL default '',
   publish integer NOT NULL default '0'
+  stamp varchar(255) NOT NULL default '',
 );
 # --------------------------------------------------------
 
diff --git a/mod/quiz/version.php b/mod/quiz/version.php
index f81de053680..c3d5ec9e1c6 100644
--- a/mod/quiz/version.php
+++ b/mod/quiz/version.php
@@ -5,7 +5,7 @@
 //  This fragment is called by moodle_needs_upgrading() and /admin/index.php
 ////////////////////////////////////////////////////////////////////////////////
 
-$module->version  = 2003082301;   // The (date) version of this module
+$module->version  = 2003082700;   // The (date) version of this module
 $module->cron     = 0;            // How often should cron check this module (seconds)?
 
 ?>