diff --git a/drivers/iio/adc/rtq6056.c b/drivers/iio/adc/rtq6056.c
index 56ed948a8ae1..8172ea51c52e 100644
--- a/drivers/iio/adc/rtq6056.c
+++ b/drivers/iio/adc/rtq6056.c
@@ -300,7 +300,7 @@ static int rtq6056_adc_read_channel(struct rtq6056_priv *priv,
 		return IIO_VAL_INT;
 	case RTQ6056_REG_SHUNTVOLT:
 	case RTQ6056_REG_CURRENT:
-		*val = sign_extend32(regval, 16);
+		*val = sign_extend32(regval, 15);
 		return IIO_VAL_INT;
 	default:
 		return -EINVAL;