Blend Mode: Masked. issue with lighting?

Hi guys,

my material using the masked blend mode appears to have it’s mask change depending on the incoming light intensity. is this a know issue or is there a workaround? http://imgur.com/0X4Saod

the effect is exaggerated eanbling Dither Opacity Mask but it still reacts to light with Dither disabled.

Could you post a screenshot of the node network driving the opacity property?