diff --git a/man2/clock_nanosleep.2 b/man2/clock_nanosleep.2
index 5070ccb41..7753db7d6 100644
--- a/man2/clock_nanosleep.2
+++ b/man2/clock_nanosleep.2
@@ -193,6 +193,10 @@ was invalid.
 .RB ( CLOCK_THREAD_CPUTIME_ID
 is not a permitted value for
 .IR clock_id .)
+.TP
+.B ENOTSUP
+The kernel does not support sleeping against this
+.IR clock_id .
 .SH VERSIONS
 The
 .BR clock_nanosleep ()
diff --git a/man2/timer_create.2 b/man2/timer_create.2
index fd366e6ea..8d9ce9c67 100644
--- a/man2/timer_create.2
+++ b/man2/timer_create.2
@@ -223,6 +223,20 @@ is invalid.
 .B ENOMEM
 .\" glibc layer: malloc()
 Could not allocate memory.
+.TP
+.B ENOTSUP
+The kernel does not support creating a timer against this
+.IR clockid .
+.TP
+.B EPERM
+.I clockid
+was
+.BR CLOCK_REALTIME_ALARM
+or
+,BR CLOCK_BOOTTIME_ALARM
+but the caller did not have the
+.BR CAP_WAKE_ALARM
+capability.
 .SH VERSIONS
 This system call is available since Linux 2.6.
 .SH CONFORMING TO
diff --git a/man2/timerfd_create.2 b/man2/timerfd_create.2
index 4b336cff5..ec137fbfe 100644
--- a/man2/timerfd_create.2
+++ b/man2/timerfd_create.2
@@ -443,6 +443,16 @@ Could not mount (internal) anonymous inode device.
 .TP
 .B ENOMEM
 There was insufficient kernel memory to create the timer.
+.TP
+.B EPERM
+.I clockid
+was
+.BR CLOCK_REALTIME_ALARM
+or
+,BR CLOCK_BOOTTIME_ALARM
+but the caller did not have the
+.BR CAP_WAKE_ALARM
+capability.
 .PP
 .BR timerfd_settime ()
 and