DHCRelay : Packet to bogus giaddr xx.xx.xx.xx

Hi

I have a Cisco router with DHCP forwarding (ip helper-address activate) connected to the WAN interface of PFSense. I have a PFsense to protect the DHCP server, and some VLAN on it with DHCP Relay activated to the same DHCP server.

The relay works for the VLAN behind PFSense. When the router send the request to the DHCP server, the PFSense relay start to work (it is not activated on WAN, nor on DHCP server VLAN, so it shouldn't). The DHCP server see a request from the Cisco and from the relay. It answer both, but PFSense don't know where to route the packet (of course, it doesn't have access to the VLAN).
There is a log : Jun 21 12:20:53 pfsense1 dhcrelay: Packet to bogus giaddr xx.xx.xx.xx.

How can I solve this ? I don't need PFSense relay to start, it should just transmit the packet.

Thanks !