diff --git a/man2/futex.2 b/man2/futex.2
index c45a7ffb1..da288a143 100644
--- a/man2/futex.2
+++ b/man2/futex.2
@@ -145,6 +145,21 @@ with another process.
 This allows the kernel to choose the fast path for validating
 the user-space address and avoids expensive VMA lookups,
 taking reference counts on file backing store, and so on.
+
+As a convenience,
+.IR <linux/futex.h>
+defines a set of constants with the suffix
+.BR _PRIVATE
+that are equivalents of all of the operations listed below,
+.\" except the obsolete FUTEX_FD for which the "private" flag was
+.\" meaningless
+but with the
+.BR FUTEX_PRIVATE_FLAG
+ORed into the constant value.
+Thus, there are
+.BR FUTEX_WAIT_PRIVATE ,
+.BR FUTEX_WAKE_PRIVATE ,
+and so on.
 .TP
 .BR FUTEX_CLOCK_REALTIME " (since Linux 2.6.28)"
 .\" commit 1acdac104668a0834cfa267de9946fac7764d486