Mind if you can help me with this error called, "Unable to cast value to Object"?

So I have been getting this error called "Unable to cast value to Object" on this script and it says the error is on Line 3 of the server script, mind if you can look over it and see if it can be fixed or maybe some changes? NOTE: A RemoteEvent is in ReplicatedStorage called, "ServerMessageEvent".

SERVER SCRIPT:

game.Players.PlayerAdded:Connect(function(player)
	wait(0.5)
	game.ReplicatedStorage.SystemMessageEvent:FireClient("[Server]: "..player.Name.." has joined the game!")
end)

LOCALSCRIPT:

game.ReplicatedStorage.SystemMessageEvent.OnClientEvent:Connect(function(message)
	game.StarterGui:SetCore("ChatMakeSystemMessage", {
		Text = message;
		Color = BrickColor.new("New Yeller").Color;
		Font = Enum.Font.Garamond;
		FontSize = Enum.FontSize.Size18;
	})
end)

creeper did a good job explaining the issue, but that's not the full answer. You need to make a loop to fire the remote event to every player, just so it goes to all players.