diff --git a/includes/class-wc-ajax.php b/includes/class-wc-ajax.php
index 7c95c3af1cc..35ebb1a61de 100644
--- a/includes/class-wc-ajax.php
+++ b/includes/class-wc-ajax.php
@@ -1482,7 +1482,7 @@ class WC_AJAX {
 
 		check_ajax_referer( 'add-order-note', 'security' );
 
-		$post_id   = (int) $_POST['post_id'];
+		$post_id   = absint( $_POST['post_id'] );
 		$note      = wp_kses_post( trim( stripslashes( $_POST['note'] ) ) );
 		$note_type = $_POST['note_type'];