diff --git a/mod/assign/locallib.php b/mod/assign/locallib.php
index 763d590aca4..a76da5319ab 100644
--- a/mod/assign/locallib.php
+++ b/mod/assign/locallib.php
@@ -5542,6 +5542,13 @@ class assign {
         $submission->status = ASSIGN_SUBMISSION_STATUS_DRAFT;
         $this->update_submission($submission, $userid, true, $this->get_instance()->teamsubmission);
 
+        // Give each submission plugin a chance to process the reverting to draft.
+        $plugins = $this->get_submission_plugins();
+        foreach ($plugins as $plugin) {
+            if ($plugin->is_enabled() && $plugin->is_visible()) {
+                $plugin->revert_to_draft($submission);
+            }
+        }
         // Update the modified time on the grade (grader modified).
         $grade = $this->get_user_grade($userid, true);
         $grade->grader = $USER->id;
@@ -5578,6 +5585,15 @@ class assign {
             $userid = required_param('userid', PARAM_INT);
         }
 
+        // Give each submission plugin a chance to process the locking.
+        $plugins = $this->get_submission_plugins();
+        $submission = $this->get_user_submission($userid, false);
+        foreach ($plugins as $plugin) {
+            if ($plugin->is_enabled() && $plugin->is_visible()) {
+                $plugin->lock($submission);
+            }
+        }
+
         $flags = $this->get_user_flags($userid, true);
         $flags->locked = 1;
         $this->update_user_flags($flags);
@@ -5695,6 +5711,14 @@ class assign {
         if (!$userid) {
             $userid = required_param('userid', PARAM_INT);
         }
+        // Give each submission plugin a chance to process the unlocking.
+        $plugins = $this->get_submission_plugins();
+        $submission = $this->get_user_submission($userid, false);
+        foreach ($plugins as $plugin) {
+            if ($plugin->is_enabled() && $plugin->is_visible()) {
+                $plugin->unlock($submission);
+            }
+        }
 
         $flags = $this->get_user_flags($userid, true);
         $flags->locked = 0;
diff --git a/mod/assign/submissionplugin.php b/mod/assign/submissionplugin.php
index 68a3da32f22..5b48a38f5b9 100644
--- a/mod/assign/submissionplugin.php
+++ b/mod/assign/submissionplugin.php
@@ -84,4 +84,32 @@ abstract class assign_submission_plugin extends assign_plugin {
     public function copy_submission( stdClass $oldsubmission, stdClass $submission) {
         return true;
     }
+
+    /*
+     * Carry out any extra processing required when the work is locked.
+     *
+     * @param stdClass $submission - assign_submission data
+     * @return void
+     */
+    public function lock(stdClass $submission) {
+    }
+
+    /**
+     * Carry out any extra processing required when the work is unlocked.
+     *
+     * @param stdClass $submission - assign_submission data
+     * @return void
+     */
+    public function unlock(stdClass $submission) {
+    }
+
+    /**
+     * Carry out any extra processing required when the work reverted to draft.
+     *
+     * @param stdClass $submission - assign_submission data
+     * @return void
+     */
+    public function revert_to_draft(stdClass $submission) {
+    }
+
 }