diff --git a/mod/assign/locallib.php b/mod/assign/locallib.php
index 73e98d7a772..2e3fec6a1c0 100644
--- a/mod/assign/locallib.php
+++ b/mod/assign/locallib.php
@@ -772,9 +772,8 @@ class assign {
                 assign_reset_gradebook($data->courseid);
 
                 // Reset revealidentities if both submissions and grades have been reset.
-                $instance = $this->get_instance();
                 if ($this->get_instance()->blindmarking && $this->get_instance()->revealidentities) {
-                    $DB->set_field('assign', 'revealidentities', 0, array('id' => $instance->id));
+                    $DB->set_field('assign', 'revealidentities', 0, array('id' => $this->get_instance()->id));
                 }
             }
         }