diff --git a/cmdline/cta-admin.1cta b/cmdline/cta-admin.1cta
index 37d5d966874809095d90c450aebd80521b22bc15..4d870ff6def7ab477b67ae7307d70088d315872b 100644
--- a/cmdline/cta-admin.1cta
+++ b/cmdline/cta-admin.1cta
@@ -126,6 +126,10 @@ Log level \fIall\fR is a synonym for "\fIdebug\fR \fIprotobuf\fR \fIprotoraw\fR"
 XRDDEBUG
 If the XRootD environment variable XRDDEBUG=1, the log level is set to \fIall\fR (see above).
 .TP
+XRDSECDEBUG
+If the XRootD environment variable XRDSECDEBUG=1, authentication messages are logged. This is useful for
+debugging problems with Kerberos or SSS authentication.
+.TP
 XRDSSIDEBUG
 If the XRootD environment variable XRDSSIDEBUG=1, debug messages will be displayed for each low-level SSI
 event.