diff --git a/share/man/man4/ahci.4 b/share/man/man4/ahci.4
index 24a277ddbf9..651b4dafd98 100644
--- a/share/man/man4/ahci.4
+++ b/share/man/man4/ahci.4
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 22, 2013
+.Dd November 2, 2018
 .Dt AHCI 4
 .Os
 .Sh NAME
@@ -162,6 +162,13 @@ fault LED device nodes
 .It Pa /dev/led/ahci*.*.locate
 locate LED device nodes
 .El
+.Sh SYSCTL
+.Bl -tag
+.It Pa dev.ahcich.X.disable_phy
+Set to 1 to disable the phy for the drive on channel X.
+Set to 0 to enable the phy.
+Useful for turning off troublemakers.
+Also useful for debugging when you need the ada drive to come and go.
 .Sh SEE ALSO
 .Xr ada 4 ,
 .Xr ata 4 ,