diff --git a/lib/libc/sys/reboot.2 b/lib/libc/sys/reboot.2
index 6805ceddceff..3629070c60d1 100644
--- a/lib/libc/sys/reboot.2
+++ b/lib/libc/sys/reboot.2
@@ -28,7 +28,7 @@
 .\"     @(#)reboot.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd September 18, 2015
+.Dd October 24, 2017
 .Dt REBOOT 2
 .Os
 .Sh NAME
@@ -84,6 +84,14 @@ for more information.
 .It Dv RB_HALT
 The processor is simply halted; no reboot takes place.
 This option should be used with caution.
+.It Dv RB_POWERCYCLE
+After halting, the shutdown code will do what it can to turn
+off the power and then turn the power back on.
+This requires hardware support, usually an auxiliary microprocessor
+that can sequence the power supply.
+At present only the
+.Xr ipmi 4
+driver implements this feature.
 .It Dv RB_POWEROFF
 After halting, the shutdown code will do what it can to turn
 off the power.
diff --git a/sys/sys/reboot.h b/sys/sys/reboot.h
index ec2a5705a1c7..9dbad4c2c4b0 100644
--- a/sys/sys/reboot.h
+++ b/sys/sys/reboot.h
@@ -60,6 +60,7 @@
 #define	RB_RESERVED2	0x80000	/* reserved for internal use of boot blocks */
 #define	RB_PAUSE	0x100000 /* pause after each output line during probe */
 #define	RB_REROOT	0x200000 /* unmount the rootfs and mount it again */
+#define	RB_POWERCYCLE	0x400000 /* Power cycle if possible */
 #define	RB_MULTIPLE	0x20000000	/* use multiple consoles */
 
 #define	RB_BOOTINFO	0x80000000	/* have `struct bootinfo *' arg */