diff --git a/src/MQTTClientMbedOs.cpp b/src/MQTTClientMbedOs.cpp
index 611e696..8c4a1fa 100644
--- a/src/MQTTClientMbedOs.cpp
+++ b/src/MQTTClientMbedOs.cpp
@@ -193,7 +193,7 @@ void MQTTClient::setDefaultMessageHandler(messageHandler mh)
     if (client != NULL) {
         client->setDefaultMessageHandler(mh);
     } else if (clientSN != NULL) {
-        client->setDefaultMessageHandler(mh);
+        clientSN->setDefaultMessageHandler(mh);
     }
 }