diff --git a/drivers/mfd/qnap-mcu.c b/drivers/mfd/qnap-mcu.c
index 4ec1f4cf902f..4cd5319fc6cb 100644
--- a/drivers/mfd/qnap-mcu.c
+++ b/drivers/mfd/qnap-mcu.c
@@ -175,8 +175,8 @@ int qnap_mcu_exec(struct qnap_mcu *mcu,
 		return -ETIMEDOUT;
 	}
 
-	crc = qnap_mcu_csum(rx, reply_data_size);
-	if (crc != rx[reply_data_size]) {
+	crc = qnap_mcu_csum(rx, reply->received - QNAP_MCU_CHECKSUM_SIZE);
+	if (crc != rx[reply->received - QNAP_MCU_CHECKSUM_SIZE]) {
 		dev_err(&mcu->serdev->dev, "Invalid Checksum received\n");
 		return -EIO;
 	}