diff --git a/mod/lesson/essay.php b/mod/lesson/essay.php
index 4767fc9..3e25b55 100644
--- a/mod/lesson/essay.php
+++ b/mod/lesson/essay.php
@@ -163,7 +163,7 @@ switch ($mode) {
                            SELECT DISTINCT userid
                              FROM {lesson_attempts}
                             WHERE lessonid = :lessonid
-                       ) ui ON u.id = ui.id", $params)) {
+                       ) ui ON u.id = ui.userid", $params)) {
                 print_error('cannotfinduser', 'lesson');
             }
         }