diff --git a/mod/workshop/lib.php b/mod/workshop/lib.php
index 31e890d55c2..f7f7773f993 100644
--- a/mod/workshop/lib.php
+++ b/mod/workshop/lib.php
@@ -244,16 +244,44 @@ function workshop_cron () {
 }
 
 /**
- * Must return an array of user records (all data) who are participants
- * for a given instance of workshop. Must include every user involved
- * in the instance, independient of his role (student, teacher, admin...)
- * See other modules as example.
+ * Returns an array of user ids who are participanting in this workshop
+ *
+ * Participants are either submission authors or reviewers or both.
+ * Authors of the example submissions and their referential assessments
+ * are not returned as the example submission is considered non-user
+ * data for the purpose of workshop backup.
  *
  * @param int $workshopid ID of an instance of this module
- * @return mixed boolean/array of students
+ * @return array of user ids, empty if there are no participants
  */
 function workshop_get_participants($workshopid) {
-    return false;
+    global $DB;
+
+    $sql = "SELECT u.id
+              FROM {workshop} w
+              JOIN {workshop_submissions} s ON s.workshopid = w.id
+              JOIN {user} u ON s.authorid = u.id
+             WHERE w.id = ? AND s.example = 0
+
+             UNION
+
+            SELECT u.id
+              FROM {workshop} w
+              JOIN {workshop_submissions} s ON s.workshopid = w.id
+              JOIN {workshop_assessments} a ON a.submissionid = s.id
+              JOIN {user} u ON a.reviewerid = u.id
+             WHERE w.id = ? AND (s.example = 0 OR a.weight = 0)";
+
+    $users = array();
+    $rs = $DB->get_recordset_sql($sql, array($workshopid, $workshopid));
+    foreach ($rs as $user) {
+        if (empty($users[$user->id])) {
+            $users[$user->id] = $user;
+        }
+    }
+    $rs->close();
+
+    return $users;
 }
 
 /**