diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index f610ad729bf3..0ac74ad92fca 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -988,7 +988,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 	struct iio_dev *idev;
 	struct at91_adc_state *st;
 	u32 reg, prop;
-	char *s;
+	const char *s;
 
 	idev = devm_iio_device_alloc(&pdev->dev, sizeof(struct at91_adc_state));
 	if (!idev)
@@ -1023,7 +1023,7 @@ static int at91_adc_probe(struct platform_device *pdev)
 
 	st->res = st->caps->high_res_bits;
 	if (st->caps->low_res_bits &&
-	    !of_property_read_string(node, "atmel,adc-use-res", (const char **)&s)
+	    !of_property_read_string(node, "atmel,adc-use-res", &s)
 	    && !strcmp(s, "lowres"))
 		st->res = st->caps->low_res_bits;