diff --git a/man7/tcp.7 b/man7/tcp.7
index 2cba03e68..7dfa425cc 100644
--- a/man7/tcp.7
+++ b/man7/tcp.7
@@ -531,6 +531,15 @@ The default value of 87380*2 bytes is lowered to 87380
 in low-memory systems.
 .RE
 .TP
+.IR tcp_slow_start_after_idle " (Boolean; default: enabled; since Linux 2.6.18)"
+.\" The following is from 2.6.28-rc4: Documentation/networking/ip-sysctl.txt
+If enabled, provide RFC 2861 behavior and time out the congestion
+window after an idle period.
+An idle period is defined as
+the current RTO (retransmission timeout).
+If disabled, the congestion window will not
+be timed out after an idle period.
+.TP
 .IR tcp_sack " (Boolean; default: enabled)"
 Enable RFC\ 2018 TCP Selective Acknowledgements.
 .TP