diff --git a/man2/fcntl.2 b/man2/fcntl.2
index 14aa7373c..50d254a02 100644
--- a/man2/fcntl.2
+++ b/man2/fcntl.2
@@ -1275,8 +1275,18 @@ Clearly,
 alone is not going to be very useful if the process holding the lock
 may live on a different machine.
 
-Before Linux 3.12, if an NFS client
-is out of contact with the server for a period of time,
+Before Linux 3.12, if an NFSv4 client
+loses contact with the server for a period of time
+(defined as more than 90 seconds with no communication),
+.\" FIXME: The 90 seconds is either /proc/fs/nfsd/nfsv4leasetime or
+.\" /proc/fs/nfsd/nfsv4gracetime. Which is it? My suspicion, looking at
+.\" fs/lockd/svcproc.c and fs/lockd/grace.c::locks_in_grace() is that
+.\" it is /proc/fs/nfsd/nfsv4gracetime that is relevant here.
+.\"
+.\" Neil Brown: With NFSv3 the failure mode is the reverse.  If
+.\"     the server loses contact with a client then any lock stays in place
+.\"     indefinitely ("why can't I read my mail"... I remember it well).
+.\"
 it might lose and regain a lock without ever being aware of the fact.
 This scenario potentially risks data corruption,
 since another process might acquire a lock in the intervening period