diff --git a/modbus.c b/modbus.c
index d743ef1..ad3d018 100644
--- a/modbus.c
+++ b/modbus.c
@@ -22,7 +22,7 @@ static unsigned char timer_state = 0;
 
 
 static uint16_t dev_id = DEFAULT_DEVICE_MODBUS_ID;
-const uint16_t com_dev_id = 247;
+static uint16_t com_dev_id = 247;
 
 static void (*ModbusUartSendByte)(USART_TypeDef*, unsigned char);
 static void (*ModbusTimEnable)(TIM_TypeDef*);