diff --git a/include/defaults.h b/include/defaults.h
index 76fbe4b..d3d9557 100644
--- a/include/defaults.h
+++ b/include/defaults.h
@@ -33,6 +33,6 @@
 #define MQTT_LWT_OFFLINE "offline"
 #define MQTT_PUBLISH_INTERVAL 5
 
-#define DTU_SERIAL 99978563412
+#define DTU_SERIAL 0x99978563412
 #define DTU_POLL_INTERVAL 5
 #define DTU_PA_LEVEL 0
\ No newline at end of file