Reverse Sprite diffuse shader lighting

[raycosantana_1]

Hi!
Im trying to make a Doom clone but while trying to use Sprite Diffuse shader I noticed the lighting in my sprites is backwards, I mean when using a directional light sprites that should be lit are dark and sprites that should be dark are lit. See Images below.

Any way I can fix this?

Thanks in advance.

[raycosantana_1]

Anyone? Please?