From LAN to service in same subnet as WAN IP fails

Greetings,

I'm trying to connect to a web service on a device with a public IP that's in the same subnet provided by the ISP as my Fortigate's WAN IP. The networks are completely separated except for the fact that they share the same ISP's subnet.

Example:

LAN device 192.168.0.100 -> Fortigate WAN 190.0.0.1/24 -> Accept: IP connection error or session timeout

Destination IP 190.0.0.2/24

In Forward Traffic Action I see:

Action     Accept: IP connection error Threat     262144 Action     Accept: session timeout Threat     262144

Thanks