diff --git a/backup/upgrade.txt b/backup/upgrade.txt
new file mode 100644
index 0000000000000..cb020956ed016
--- /dev/null
+++ b/backup/upgrade.txt
@@ -0,0 +1,17 @@
+This files describes API changes in /backup/*,
+information provided here is intended especially for developers.
+
+=== 2.4 ===
+
+* Since 2.3.1+ the backup file name schema has changed. The ID of the course will always be part of
+    the filename regardless of the setting 'backup_shortname'. See MDL-33812.
+
+=== 2.3 ===
+
+* Since 2.3.1+ the backup file name schema has changed. The ID of the course will always be part of
+    the filename regardless of the setting 'backup_shortname'. See MDL-33812.
+
+=== 2.2 ===
+
+* Since 2.2.4+ the backup file name schema has changed. The ID of the course will always be part of
+    the filename regardless of the setting 'backup_shortname'. See MDL-33812.
\ No newline at end of file
diff --git a/backup/util/dbops/backup_plan_dbops.class.php b/backup/util/dbops/backup_plan_dbops.class.php
index e169a8a8ba130..2e2faaeb05e4e 100644
--- a/backup/util/dbops/backup_plan_dbops.class.php
+++ b/backup/util/dbops/backup_plan_dbops.class.php
@@ -197,19 +197,19 @@ public static function get_mnet_localhost_wwwroot() {
     * @param int $courseid/$sectionid/$cmid
     * @param bool $users Should be true is users were included in the backup
     * @param bool $anonymised Should be true is user information was anonymized.
-    * @param bool $useidasname true to use id, false to use strings (default)
+    * @param bool $useidonly only use the ID in the file name
     * @return string The filename to use
     */
-    public static function get_default_backup_filename($format, $type, $id, $users, $anonymised, $useidasname = false) {
+    public static function get_default_backup_filename($format, $type, $id, $users, $anonymised, $useidonly = false) {
         global $DB;
 
         // Calculate backup word
         $backupword = str_replace(' ', '_', textlib::strtolower(get_string('backupfilename')));
         $backupword = trim(clean_filename($backupword), '_');
 
+        // Not $useidonly, lets fetch the name
         $shortname = '';
-        // Not $useidasname, lets calculate it, else $id will be used
-        if (!$useidasname) {
+        if (!$useidonly) {
             // Calculate proper name element (based on type)
             switch ($type) {
                 case backup::TYPE_1COURSE:
@@ -231,7 +231,11 @@ public static function get_default_backup_filename($format, $type, $id, $users,
             $shortname = textlib::strtolower(trim(clean_filename($shortname), '_'));
         }
 
-        $name = empty($shortname) ? $id : $shortname;
+        // The name will always contain the ID, but we append the course short name if requested.
+        $name = $id;
+        if (!$useidonly && $shortname != '') {
+            $name .= '-' . $shortname;
+        }
 
         // Calculate date
         $backupdateformat = str_replace(' ', '_', get_string('backupnameformat', 'langconfig'));
diff --git a/backup/util/helper/backup_cron_helper.class.php b/backup/util/helper/backup_cron_helper.class.php
index a974883a5279d..e3ada4f6b0d82 100644
--- a/backup/util/helper/backup_cron_helper.class.php
+++ b/backup/util/helper/backup_cron_helper.class.php
@@ -561,18 +561,7 @@ public static function remove_excess_backups($course) {
         if (!empty($dir) && ($storage == 1 || $storage == 2)) {
             // Calculate backup filename regex, ignoring the date/time/info parts that can be
             // variable, depending of languages, formats and automated backup settings
-
-
-            // MDL-33531: use different filenames depending on backup_shortname option
-            if ( !empty($config->backup_shortname) ) {
-                $context = get_context_instance(CONTEXT_COURSE, $course->id);
-                $courseref = format_string($course->shortname, true, array('context' => $context));
-                $courseref = str_replace(' ', '_', $courseref);
-                $courseref = textlib::strtolower(trim(clean_filename($courseref), '_'));
-            } else {
-                $courseref = $course->id;
-            }
-            $filename = $backupword . '-' . backup::FORMAT_MOODLE . '-' . backup::TYPE_1COURSE . '-' .$courseref . '-';
+            $filename = $backupword . '-' . backup::FORMAT_MOODLE . '-' . backup::TYPE_1COURSE . '-' .$course->id . '-';
             $regex = '#^'.preg_quote($filename, '#').'.*\.mbz$#';
 
             // Store all the matching files into fullpath => timemodified array
diff --git a/lang/en/admin.php b/lang/en/admin.php
index 7f8972a8564de..5e7b0d9826457 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -68,7 +68,7 @@
 $string['backgroundcolour'] = 'Transparent colour';
 $string['backups'] = 'Backups';
 $string['backup_shortname'] = 'Use course name in backup filename';
-$string['backup_shortnamehelp'] = 'Use the course name as part of the backup filename instead of the course id number.';
+$string['backup_shortnamehelp'] = 'Use the course name as part of the backup filename.';
 $string['badwordsconfig'] = 'Enter your list of bad words separated by commas.';
 $string['badwordsdefault'] = 'If the custom list is empty, a default list from the language pack will be used.';
 $string['badwordslist'] = 'Custom bad words list';