diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index ea5ca163d879..c4de706012e5 100644
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -1377,7 +1377,8 @@ static int at91_adc_read_info_raw(struct iio_dev *indio_dev,
 		*val = st->conversion_value;
 		ret = at91_adc_adjust_val_osr(st, val);
 		if (chan->scan_type.sign == 's')
-			*val = sign_extend32(*val, 11);
+			*val = sign_extend32(*val,
+					     chan->scan_type.realbits - 1);
 		st->conversion_done = false;
 	}