Unsocket cube recipe not work on unique?

I never felt the need to try this cube recipe before, but today I tried to remove a sapphire from my goldskin armor...

Hel + Tome of teleport + socketed item = no joy in this case.

Am I doing something wrong or does this recipe simply not work on uniques? Perhaps a bug or change in code?

V1.13 ladder btw.

Thanks.|||It's not tome of teleport, you need a town portal scroll |||Oh yeah! Happiness achieved! Thanks!