diff --git a/src/cm_mes/mes_tcp.h b/src/cm_mes/mes_tcp.h
index 6fa6d0751e0e7c8e3b01f2851cc59825875a74b3..199841abd89c0ccfe408b2087377fcf1c5ab3549 100644
--- a/src/cm_mes/mes_tcp.h
+++ b/src/cm_mes/mes_tcp.h
@@ -39,7 +39,7 @@ extern "C" {
 #define MES_INSTANCE_ID(id)         (uint8)((id) >> UINT8_BITS)
 #define MES_CHANNEL_ID(id)          (uint8)((id)&0x00FF)
 #define MES_CONNECT_CMD             (uint8)(CM_MAX_MES_MSG_CMD + 1)
-#define MES_HEARTBEAT_CMD           (uint8)(255)
+#define MES_HEARTBEAT_CMD           (uint8)(254)
 #define MES_HEARTBEAT_INTERVAL      (1)