class of service does not work on vpls interface?

Hi all,

I want to rewrite all egress traffic with CoS:4 at ge-0/0/0.34. Here's my configuration:

interfaces {
    ge-0/0/0 {
        per-unit-scheduler;
        vlan-tagging;
        encapsulation flexible-ethernet-services;
        mac xx.xx.xx.xx.xx.xx;          
        unit 34 {                       
            encapsulation vlan-vpls;    
            vlan-id 34;                 
            family vpls;                
        }                               
        unit 35 {                       
            vlan-id 35;                 
            family inet {               
                dhcp {                  
                    client-identifier ascii juniper;
                    vendor-id juniper;  
                }                       
            }                           
        }                               
    }
    ge-0/0/3 {
        flexible-vlan-tagging;
        native-vlan-id 34;
        encapsulation extended-vlan-vpls;
        unit 34 {
            vlan-id 34;
            family vpls;
        }
    }
class-of-service {
    host-outbound-traffic {
        ieee-802.1;
    }
    interfaces {
        ge-0/0/0 {
            unit 34 {
                classifiers {
                    ieee-802.1 default;
                }
                rewrite-rules {
                    ieee-802.1 IPTV-Rewriter vlan-tag outer;
                }
            }
        }
    }
    rewrite-rules {
        ieee-802.1 IPTV-Rewriter {
            import default;
            forwarding-class best-effort {
                loss-priority low code-point 100;
                loss-priority high code-point 100;
            }
            forwarding-class expedited-forwarding {
                loss-priority high code-point 100;
                loss-priority low code-point 100;
            }
            forwarding-class network-control {
                loss-priority low code-point 100;
                loss-priority high code-point 100;
            }                           
            forwarding-class assured-forwarding {
                loss-priority high code-point 100;
            }                           
        }                               
    }                                   
}                                       

I confirmed the VPLS part works, because I can see the DHCP traffic send from a device connected to ge-0/0/3 at ge-0/0/0. But VLAN PRI value of those packets are always 0. It looks like my rewrite rule applied to ge-0/0/0.34 never worked.