Kayn in game rune change from Preditor to Electrocute

As the title says, I i choose runes with preditor rune in it, after the loading screen there will be a line of text in chat (white) that preditor was changed to electrocute. Wich implies that out of all champions Kayn is forbidden to use the Preditor rune. Would very much like to get the attention of a Riot employee so this bug could be fixed.