diff --git a/bin/nsupdate/nsupdate.rst b/bin/nsupdate/nsupdate.rst
index 17ab96d421..b91a606845 100644
--- a/bin/nsupdate/nsupdate.rst
+++ b/bin/nsupdate/nsupdate.rst
@@ -216,6 +216,8 @@ The command formats and their meanings are as follows:
    update requests are sent. If no port number is specified, the default
    DNS port number of 53 is used.
 
+   .. note:: This command has no effect when GSS-TSIG is in use.
+
 ``local address port``
    This command sends all dynamic update requests using the local ``address``. When
    no local statement is provided, :program:`nsupdate` sends updates using
diff --git a/doc/man/nsupdate.1in b/doc/man/nsupdate.1in
index d83bd49ccd..fa86e27edf 100644
--- a/doc/man/nsupdate.1in
+++ b/doc/man/nsupdate.1in
@@ -243,6 +243,13 @@ zone\(aqs SOA record identify the primary server for that zone.
 \fBport\fP is the port number on \fBservername\fP where the dynamic
 update requests are sent. If no port number is specified, the default
 DNS port number of 53 is used.
+.sp
+\fBNOTE:\fP
+.INDENT 7.0
+.INDENT 3.5
+This command has no effect when GSS\-TSIG is in use.
+.UNINDENT
+.UNINDENT
 .TP
 .B \fBlocal address port\fP
 This command sends all dynamic update requests using the local \fBaddress\fP\&. When