Active Passive HA but still having a loop

[kobozo]

I have 2 90d in active-passive HA mode.

I also have 2 layer3 switches

active fortinet port 11 goes to switch 1

active fortinet port 12 goes to switch 2

no problem so far

passive fortinet port 11 goes to switch 1

still no problem

passive fortinet port 12 goes to switch 2

loop

port 11 & 12 are both in a hardware switch conf with 3 vlan underneath

the physical switches are not interconnected