diff --git a/usr.sbin/ntp/doc/ntpd.8 b/usr.sbin/ntp/doc/ntpd.8
index a55fe43de299..069ef4266eef 100644
--- a/usr.sbin/ntp/doc/ntpd.8
+++ b/usr.sbin/ntp/doc/ntpd.8
@@ -1,7 +1,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 17, 2006
+.Dd May 18, 2010
 .Dt NTPD 8
 .Os
 .Sh NAME
@@ -108,6 +108,9 @@ Specify the name and path of the configuration file, default
 Specify debugging mode.
 This option may occur more than once,
 with each occurrence indicating greater detail of display.
+You need to compile
+.Nm
+with DEBUG in order to use this.
 .It Fl D Ar level
 Specify debugging level directly.
 .It Fl f Ar driftfile