diff --git a/xCAT-server/lib/xcat/plugins/pxe.pm b/xCAT-server/lib/xcat/plugins/pxe.pm
index 8fadc1e3e..24bec99af 100644
--- a/xCAT-server/lib/xcat/plugins/pxe.pm
+++ b/xCAT-server/lib/xcat/plugins/pxe.pm
@@ -129,7 +129,7 @@ sub setstate {
             $kcmdlinehack =~ s/#TABLE:([^:#]+):([^:#]+):([^:#]+)#/$naval/;
         } else {
             my $msg =  "Table key of $2 not yet supported by boottarget mini-template";
-            $callback->({
+            $::callback->({
                 error => ["$msg"],
                 errorcode => [1]
             });
@@ -148,7 +148,7 @@ sub setstate {
       unless ($ipfn) {
         my @myself = xCAT::NetworkUtils->determinehostname();
         my $myname = $myself[(scalar @myself)-1];
-         $callback->(
+         $::callback->(
                 {
                  error => [
                      "$myname: Unable to determine or reasonably guess the image server for $node"
@@ -357,6 +357,7 @@ sub process_request {
   $request = shift;
   $callback = shift;
   my $sub_req = shift;
+  $::callback=$callback;
   my @args;
   my @nodes;
   my @rnodes;
diff --git a/xCAT-server/lib/xcat/plugins/yaboot.pm b/xCAT-server/lib/xcat/plugins/yaboot.pm
index 2ee83de4e..e305ecfde 100644
--- a/xCAT-server/lib/xcat/plugins/yaboot.pm
+++ b/xCAT-server/lib/xcat/plugins/yaboot.pm
@@ -104,7 +104,7 @@ sub setstate {
                   if (xCAT::InstUtils->is_me($sn)) {
                       my @myself = xCAT::NetworkUtils->determinehostname();
                       my $myname = $myself[(scalar @myself)-1];
-                      $callback->(
+                      $::callback->(
                           {
                           error => [
                           "$myname: Unable to determine the image server for $node on service node $sn"
@@ -116,7 +116,7 @@ sub setstate {
                   }
               }
           } else {
-              $callback->(
+              $::callback->(
                           {
                           error => [
                           "$myname: Unable to determine the image server for $node"
@@ -408,6 +408,7 @@ sub preprocess_request {
 sub process_request {
   $request = shift;
   $callback = shift;
+  $::callback=$callback;
   $sub_req = shift;
   my $command  = $request->{command}->[0];
   %breaknetbootnodes=();