diff --git a/man2/futex.2 b/man2/futex.2
index b24524975..b481c452d 100644
--- a/man2/futex.2
+++ b/man2/futex.2
@@ -785,6 +785,14 @@ bit is set.
 .\"       the man page.
 .\" FIXME And *how* does FUTEX_TRYLOCK_PI deal with this situation?
 User space cannot handle this race free.
+
+The
+.IR uaddr2 ,
+.IR val ,
+.IR timeout ,
+and
+.IR val3
+arguments are ignored.
 .TP
 .BR FUTEX_UNLOCK_PI " (since Linux 2.6.18)"
 .\" commit c87e2837be82df479a6bae9f155c43516d2feebc