diff --git a/pkgs/nixfiles/nixfiles-system-sync-to-hydra.sh b/pkgs/nixfiles/nixfiles-system-sync-to-hydra.sh
index c6f83a0..3111fe7 100755
--- a/pkgs/nixfiles/nixfiles-system-sync-to-hydra.sh
+++ b/pkgs/nixfiles/nixfiles-system-sync-to-hydra.sh
@@ -2,6 +2,21 @@
 
 set -euo pipefail
 
+ALLOW_REBOOT=
+
+while [[ $# -gt 0 ]]; do
+	case $1 in
+		--allow-reboot)
+			ALLOW_REBOOT=1
+			shift
+			;;
+		*)
+			echo "Unknown option $1"
+			exit 1
+			;;
+	esac
+done
+
 HYDRA_JOB_URL="https://hydra.clerie.de/job/nixfiles/nixfiles/nixosConfigurations.$(hostname)/latest-finished"
 
 echo "Fetching job output from ${HYDRA_JOB_URL}"
@@ -13,7 +28,25 @@ nix copy --from "https://nix-cache.clerie.de" "${STORE_PATH}"
 echo "Add to system profile"
 nix-env -p "/nix/var/nix/profiles/system" --set "${STORE_PATH}"
 
-echo "Activate system"
-/nix/var/nix/profiles/system/bin/switch-to-configuration switch
+echo "Set as boot target"
+/nix/var/nix/profiles/system/bin/switch-to-configuration boot
+
+BOOTED_SYSTEM_KERNEL="$(readlink /run/booted-system/{initrd,kernel,kernel-modules})"
+ACTIVATING_SYSTEM_KERNEL="$(readlink /nix/var/nix/profiles/system/{initrd,kernel,kernel-modules})"
+
+if [[ "$BOOTED_SYSTEM_KERNEL" != "$ACTIVATING_SYSTEM_KERNEL" ]]; then
+	echo "Reboot is required"
+	if [[ -n "$ALLOW_REBOOT" ]]; then
+		echo "Rebooting system now"
+		shutdown -r +1 "System update requires reboot"
+	else
+		echo "Automatic reboot not allowed (maybe use --allow-reboot next time)"
+		echo "The system upgrade is staged, please reboot manually soon"
+	fi
+else
+	echo "No reboot is required"
+	echo "Activating system now"
+	/nix/var/nix/profiles/system/bin/switch-to-configuration switch
+fi
 
 echo "Finished system upgrade"