diff --git a/includes/class-psa-upgrade.php b/includes/class-psa-upgrade.php
index b1f20b4..643fa2b 100644
--- a/includes/class-psa-upgrade.php
+++ b/includes/class-psa-upgrade.php
@@ -16,6 +16,8 @@
  * @package PeptideSearchAI
  */
 
+declare( strict_types=1 );
+
 if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }