diff --git a/drivers/mfd/rn5t618.c b/drivers/mfd/rn5t618.c
index da5cd9c92a59..ead2e79036a9 100644
--- a/drivers/mfd/rn5t618.c
+++ b/drivers/mfd/rn5t618.c
@@ -26,6 +26,7 @@ static bool rn5t618_volatile_reg(struct device *dev, unsigned int reg)
 	case RN5T618_WATCHDOGCNT:
 	case RN5T618_DCIRQ:
 	case RN5T618_ILIMDATAH ... RN5T618_AIN0DATAL:
+	case RN5T618_ADCCNT3:
 	case RN5T618_IR_ADC1 ... RN5T618_IR_ADC3:
 	case RN5T618_IR_GPR:
 	case RN5T618_IR_GPF: