diff --git a/src/Symfony/Component/Notifier/Bridge/Smsapi/SmsapiTransport.php b/src/Symfony/Component/Notifier/Bridge/Smsapi/SmsapiTransport.php
index 700447dfdf3a7..e45ae6c0d1c3c 100644
--- a/src/Symfony/Component/Notifier/Bridge/Smsapi/SmsapiTransport.php
+++ b/src/Symfony/Component/Notifier/Bridge/Smsapi/SmsapiTransport.php
@@ -64,6 +64,7 @@ protected function doSend(MessageInterface $message): SentMessage
                 'to' => $message->getPhone(),
                 'message' => $message->getSubject(),
                 'format' => 'json',
+                'encoding' => 'utf-8',
             ],
         ]);