diff --git a/xCAT-server/lib/xcat/plugins/dhcp.pm b/xCAT-server/lib/xcat/plugins/dhcp.pm
index 4bbd6cc3a..ba10c60f6 100644
--- a/xCAT-server/lib/xcat/plugins/dhcp.pm
+++ b/xCAT-server/lib/xcat/plugins/dhcp.pm
@@ -1147,7 +1147,7 @@ sub process_request
             }
         }
         close($omshell) if ($^O ne 'aix');
-        close($omshell6) if ($^O ne 'aix');
+        close($omshell6) if ($omshell6 and $^O ne 'aix');
         foreach my $node (@{$req->{node}})
         {
             unless ($machash)