diff --git a/drivers/hwmon/smsc47m1.c b/drivers/hwmon/smsc47m1.c
index cc6aca6e436c..b637836b58a1 100644
--- a/drivers/hwmon/smsc47m1.c
+++ b/drivers/hwmon/smsc47m1.c
@@ -351,6 +351,8 @@ static ssize_t fan_div_store(struct device *dev,
 		tmp |= data->fan_div[2] << 4;
 		smsc47m1_write_value(data, SMSC47M2_REG_FANDIV3, tmp);
 		break;
+	default:
+		BUG();
 	}
 
 	/* Preserve fan min */