Dual PPPoE Clients on single port

Hi Folks

I try to use 2 PPPoE clients on one physical Interface
First

/interface pppoe-client
add add-default-route=yes default-route-distance=10 disabled=no interface=\
    ether1-out keepalive-timeout=60 max-mru=1480 max-mtu=1480 mrru=1600 name=\
    pppoe-out1 password=XXX use-peer-dns=yes user=XXX1

and second

/interface pppoe-client
add interface=ether1-out keepalive-timeout=60 max-mru=1480 max-mtu=1480 mrru=\
    1600 name=pppoe-out2 password=DDDD profile=profile1 user=DDDD2

But when pppoe-out2 activates pppoe-out1 goes inactive.
If I disable pppoe-out2 then pppoe-out1 activates normally but seems that two pppoe clients could not work simultaneously.

How can I make them both work ?

Thanx!