diff --git a/man2/reboot.2 b/man2/reboot.2
index e307b1f2b..ae0b7780f 100644
--- a/man2/reboot.2
+++ b/man2/reboot.2
@@ -162,6 +162,26 @@ For the i386 architecture, the additional argument does not do
 anything at present (2.1.122), but the type of reboot can be
 determined by kernel command-line arguments ("reboot=...") to be
 either warm or cold, and either hard or through the BIOS.
+.SS Behavior inside PID namespaces
+.\" commit commit 923c7538236564c46ee80c253a416705321f13e3
+Since Linux 3.9, when
+.BR reboot ()
+is called from a PID namespace (see
+.BR pid_namespaces (7))
+other than the initial PID namespace,
+the effect of the call is to send a signal to the namespace "init" process.
+.BR LINUX_REBOOT_CMD_RESTART
+and
+.BR LINUX_REBOOT_CMD_RESTART2
+cause a
+.BR SIGHUP
+signal to be sent.
+.BR LINUX_REBOOT_CMD_POWER_OFF
+and
+.BR LINUX_REBOOT_CMD_HALT
+cause a
+.B SIGINT
+signal to be sent.
 .SH RETURN VALUE
 For the values of
 .I cmd