Bug highlightlayer + sprite transparency

Hi !

I noticed a bug with the hightlight layer and the sprite transparency, if the sprite overlapse the highlight object, the sprite take the color of the layer. 
I tried to add the sprite to another renderingId but it was the same !

I attach a screen and a playground ( http://www.babylonjs-playground.com/#1UJAM6 )  to test !

Thanks for the answers !