diff --git a/src/export.php b/src/export.php
index 0d7d83e..8a3b9bf 100644
--- a/src/export.php
+++ b/src/export.php
@@ -14,7 +14,7 @@ $db = DBConnection::instance();
 $listData = $db->sqa("SELECT * FROM {$db->prefix}lists WHERE id=$listId");
 if ( $listData && !is_logged() && !$listData['published'] ) {
     $extra = json_decode($listData['extra'] ?? '', true, 10, JSON_INVALID_UTF8_SUBSTITUTE);
-    $feedKey = (string)$extra['feedKey'] ?? '';
+    $feedKey = (string) ($extra['feedKey'] ?? '');
     $inFeedKey = trim(_get('key'));
     if ($feedKey == '' || $feedKey != $inFeedKey) {
         die("Access denied.");
diff --git a/src/feed.php b/src/feed.php
index 356af99..2f9d896 100644
--- a/src/feed.php
+++ b/src/feed.php
@@ -17,7 +17,7 @@ $db = DBConnection::instance();
 $listData = $db->sqa("SELECT * FROM {$db->prefix}lists WHERE id=$listId");
 if ( $listData && need_auth() && !$listData['published'] ) {
     $extra = json_decode($listData['extra'] ?? '', true, 10, JSON_INVALID_UTF8_SUBSTITUTE);
-    $feedKey = (string)$extra['feedKey'] ?? '';
+    $feedKey = (string) ($extra['feedKey'] ?? '');
     $inFeedKey = trim(_get('key'));
     if ($feedKey == '' || $feedKey != $inFeedKey) {
         die("Access denied!<br> List is not published.");
diff --git a/src/includes/api/ListsController.php b/src/includes/api/ListsController.php
index 52f4ab3..3aac2b1 100644
--- a/src/includes/api/ListsController.php
+++ b/src/includes/api/ListsController.php
@@ -189,7 +189,7 @@ class ListsController extends ApiController {
                 error_log("Failed to decodes JSON data of list extra listId=". (int)$row['id'] . ": " . json_last_error_msg());
                 $extra = [];
             }
-            $feedKey = (string)$extra['feedKey'] ?? '';
+            $feedKey = (string) ($extra['feedKey'] ?? '');
         }
 
         return array(