Portal: npc_rocket_turret can see portals through walls

[taco]

The Setup:
There is an npc_rocket_turret at one end of a room and portable wall at the other end of the room.

The Problem:
If I place a portal up high on the portable wall and then stand in front of the turret, the turret will sometimes attempt to fire a missile that passes through me AND the portal (ie. it fires on an upward angle); however, I want the turret to fire directly at the player.

Even if I put a solid wall between the portalable wall and the turret, the turret still "knows" that the portal is there and attempts to make the same shot. I have also tried using the Block LOS tool material.

It will fire at the player properly if the portal isn't up there, but for this puzzle I am making, it needs to be there.

Can you help?
Any ideas on how to get the turret to ignore the portal or to focus directly on the player would be a lot of help.