aiShadowMatte additive reflections

[atlanteanpictures]

Hi, I'm trying to create a reflection of a backlit object on an aiShadowMatte material, I remember in maya 2017, the aiShadowCatcher was great and allowed me to not only render the reflection correctly over my backplate, but also gave me a reflection matte AOV. In the new aiShadowMatte shader the reflection seems only to be additive which means if you have a dark object reflecting in a surface it will not cut out the light from behind the object correctly and also cannot be overed in a comp correctly any more.

Is there something I have missed or is this now broken in the current versions of arnold?

Attached is a screenshot of the problem, as mentioned this worked fine in earlier versions of arnold using the aiShadowCatcher.

Thanks

Danieladditive-reflection.jpg