diff --git a/configs/arcbox-arm64.config b/configs/arcbox-arm64.config
index 96a53f6..8c64ff5 100644
--- a/configs/arcbox-arm64.config
+++ b/configs/arcbox-arm64.config
@@ -220,6 +220,17 @@ CONFIG_VIRTIO_IOMMU=y
 CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_VIRTIO=y
 
+# RTC: PL031 on the custom HV backend (ABX-416). HCTOSYS sets
+# CLOCK_REALTIME from rtc0 at boot, so the guest has correct wall time
+# before the agent is up (TLS validation during early boot). SYSTOHC is
+# off: the virtual RTC mirrors the host wall clock, so the guest must
+# not write NTP-adjusted time back into it (one-way, RTC -> system).
+CONFIG_RTC_CLASS=y
+CONFIG_RTC_HCTOSYS=y
+CONFIG_RTC_HCTOSYS_DEVICE="rtc0"
+# CONFIG_RTC_SYSTOHC is not set
+CONFIG_RTC_DRV_PL031=y
+
 # Multi-device (RAID/LVM) and Device Mapper
 CONFIG_MD=y
 CONFIG_BLK_DEV_DM=y