diff --git a/perl-xCAT/xCAT/Usage.pm b/perl-xCAT/xCAT/Usage.pm
index 1a49d3a3f..b66003fa6 100644
--- a/perl-xCAT/xCAT/Usage.pm
+++ b/perl-xCAT/xCAT/Usage.pm
@@ -185,7 +185,7 @@ my %usage = (
    PPC specific:
        getmacs <noderange> [-F filter] 
        getmacs <noderange> [-M]
-       getmacs <noderange> [-V| --verbose] [-f] [-d] [--arp] | [-D [-S server] [-G gateway] [-C client]]
+       getmacs <noderange> [-V| --verbose] [-f] [-d] [--arp] | [-D [-o] [-S server] [-G gateway] [-C client]]
    blade specific:
        getmacs <noderange> [-V| --verbose] [-d] [--arp] [-i ethN|enN]
 ",