diff --git a/src/ClientBase.php b/src/ClientBase.php
index 9692022..deb0bd3 100644
--- a/src/ClientBase.php
+++ b/src/ClientBase.php
@@ -66,7 +66,7 @@ public function execute($method, array $arguments = []): object
 
         $response = json_decode($json_response);
 
-        if($response->s === 'error') {
+        if(isset($response->s) && $response->s === 'error') {
             throw new ApiException(message: $response->errmsg, response: $response);
         }