Stop Unity from extrapolating extra Image Texture information

Heya mates,

Does anyone know how to prevent Unity from adding this extra texture information in the image’s alpha zone? Importing as a PNG and Unity generates extra colour info in the alpha areas by stretching out the last pixel to the edge of the frame

Probably super useful in most cases but in this instance I need it to remain black

This is commonly referred as texture/pixel/edge padding
http://wiki.polycount.com/wiki/Edge_padding
It is an important feature indeed.

Someone will surely be able to help you control or disable it but for that to happen you need to be more specific on where this happens in the asset workflow exactly.