Rarity rolls on an already rare item

[Eleraan 354]

Odd question but if you were to get a rarity roll on improving a rare item and it succeeded does it go Supreme or are rarity rolls on already rare+ items just a waste/not possible? 

[Xallo 2,599]

They have a chance of going supreme or fantastic if you do not fail the improvement action, and are lucky. 

[Eleraan 354]

Ahh interesting. Thanks.