diff --git a/oe_authentication.post_update.php b/oe_authentication.post_update.php
new file mode 100644
index 0000000..0cc73c1
--- /dev/null
+++ b/oe_authentication.post_update.php
@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * @file
+ * Post update functions for OE Authentication module.
+ */
+
+declare(strict_types = 1);
+
+/**
+ * Add the 'block_on_site_admin_approval' module setting.
+ */
+function oe_authentication_post_update_user_register_redirect(): void {
+  \Drupal::configFactory()->getEditable('oe_authentication.settings')
+    ->set('block_on_site_admin_approval', TRUE)
+    ->save();
+}