diff --git a/man2/futex.2 b/man2/futex.2
index 61f1b1bcb..4d9b59f24 100644
--- a/man2/futex.2
+++ b/man2/futex.2
@@ -760,6 +760,13 @@ Try again.
 .\"           futex_requeue() ==> futex_proxy_trylock_atomic() ==> 
 .\"               futex_lock_pi_atomic() ==> attach_to_pi_owner() ==> EAGAIN?
 .TP
+.BR EDEADLK
+.RB ( FUTEX_LOCK_PI ,
+.BR FUTEX_TRYLOCK_PI )
+The futex at
+.I uaddr
+is already locked by the caller.
+.TP
 .B EFAULT
 A required pointer argument (i.e.,
 .IR uaddr ,