diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index 7e2192870743..533667eefe41 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -476,6 +476,10 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 		 * byte set to zero. */
 		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
 		break;
+
+	default:
+		dev_err_ratelimited(&indio_dev->dev, "Unsupported reg_size: %u\n", reg_size);
+		goto irq_handled;
 	}
 
 	/*