I don't know the exact name of this perk, and maybe its just a bug, but certain Light Armors have problems with it (with different characters). Like the Thieves Guildmaster armor doesn't acquire a bonus from it, but Nightingale armor does.

Anyway to fix this? With a patch or otherwise? I don't really know what to do other than not wear it (its one of the cooler looking armors in the game).