diff --git a/man7/tcp.7 b/man7/tcp.7
index fadfd41b7..2712e2811 100644
--- a/man7/tcp.7
+++ b/man7/tcp.7
@@ -435,14 +435,27 @@ will allocate.
 This value overrides any other limits
 imposed by the kernel.
 .TP
+.IR tcp_mtu_probing " (integer; default: 0; since Linux 2.6.17)"
+.\" The following is from 2.6.28-rc4: Documentation/networking/ip-sysctl.txt
+This parameter controls TCP Packetization-Layer Path MTU Discovery.
+The following values may be assigned to the file:
+.RS
+.IP 0 3
+Disabled
+.IP 1
+Disabled by default, enabled when an ICMP black hole detected
+.IP 2
+Always enabled, use initial MSS of
+.IR tcp_base_mss .
+.RE
+.TP
 .IR tcp_no_metrics_save " (Boolean; default: disabled; since Linux 2.6.6)"
 .\" The following is from 2.6.28-rc4: Documentation/networking/ip-sysctl.txt
 By default, TCP saves various connection metrics in the route cache
 when the connection closes, so that connections established in the
 near future can use these to set initial conditions.
 Usually, this increases overall performance,
-but it may sometimes cause performance
-degradation.
+but it may sometimes cause performance degradation.
 If
 .I tcp_no_metrics_save
 is enabled, TCP will not cache metrics on closing connections.