I was using MarketplaceService:PlayerOwnsAsset to check to see if players bought paid access to my place, and got an unrelated warning in my output.
print(Game:GetService("MarketplaceService"):PlayerOwnsAsset(Game.Players.Player1, 4321846))
Output: MarketplaceService:PromptPurchase() was called on a guest, please use this call only on players with an account.
Whimzee
(Whimzee)
2
Every player with a negative userId counts as a guest. You can only use :PlayerOwnsAsset() in a game server.
Goldamass
(Goldamass)
3
It’s just a warning and it’s there for a reason.
I don’t see the reason to warn me about a method I’m not using.
I don’t see the reason to warn me about a method I’m not using.[/quote]
You must have used it somewhere in the place, else they have just forgot to change the text on the warning 
Whoops, looks like a typo! We’ll fix that.
Ok this has been fixed, but it will still warn you! It just won’t sound so stupid 