Love potion - Friends Buff

Hello everyone,

I've sent my brother a gift "Love Potion" so he could buff my Mayor's House.
He received it, it is in the star menu, but he can't use it - when he visits my map and selects it in the star menu on my map, mayor house doesn't light up as it does when he is on his map or as the other buildings light up when using other buffs regular from provision house or those for gems like Red Flying Settler.

I guess this must be a bug, because it is a buff like others I've mentioned, so it should be applicable...also there was no mentioning in the trader item that this cannot be used as friends buff, is it?

Thanks in advance.

PS - I've used search before posting; I didn't find anyone with the same problem.

True. You could use love potion, cheese sandwich and drilled plan only on you're own mayor house.
And i agree with you, this info should stand also in the gem-shop tooltips.