diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 5d597e5050f6820c598777cf6da677196c202322..1b4b3203e42858b7a36e1bdfdcf83696a1b1f809 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -91,7 +91,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
 	int ret;
 	int i;
 	int bits_per_word = ad7949_adc->resolution;
-	int mask = GENMASK(ad7949_adc->resolution, 0);
+	int mask = GENMASK(ad7949_adc->resolution - 1, 0);
 	struct spi_message msg;
 	struct spi_transfer tx[] = {
 		{