diff --git a/lib/mqtt_msg.c b/lib/mqtt_msg.c
index f6f983e..27dcdea 100644
--- a/lib/mqtt_msg.c
+++ b/lib/mqtt_msg.c
@@ -568,15 +568,16 @@ int mqtt_has_valid_msg_hdr(uint8_t *buffer, uint32_t length)
     switch (mqtt_get_type(buffer)) {
     case MQTT_MSG_TYPE_CONNECT:
     case MQTT_MSG_TYPE_CONNACK:
-    case MQTT_MSG_TYPE_PUBACK:
     case MQTT_MSG_TYPE_PUBREC:
     case MQTT_MSG_TYPE_PUBCOMP:
-    case MQTT_MSG_TYPE_SUBACK:
-    case MQTT_MSG_TYPE_UNSUBACK:
     case MQTT_MSG_TYPE_PINGREQ:
     case MQTT_MSG_TYPE_PINGRESP:
     case MQTT_MSG_TYPE_DISCONNECT:
         return (buffer[0] & 0x0f) == 0;  /* all flag bits are 0 */
+    case MQTT_MSG_TYPE_SUBACK:
+    case MQTT_MSG_TYPE_PUBACK:
+    case MQTT_MSG_TYPE_UNSUBACK:
+        return ((buffer[0] & 0x0f) == 0x02) || ((buffer[0] & 0x0f) == 0x0);  /* Non standard Thingboard headers */
     case MQTT_MSG_TYPE_PUBREL:
     case MQTT_MSG_TYPE_SUBSCRIBE:
     case MQTT_MSG_TYPE_UNSUBSCRIBE: