A part of my custom teleport GUI script isn't working?

So the teleportation portion works fine, and the custom GUI pops up and it takes me to the place and everything. My problem is that ROBLOX's Default GUI (You know, the one with a message that says "Teleporting to place...") still shows up. This is in a normal script (Not LocalScript) in ServerScriptService.

This works in Solo/Test mode, but not in online.

repeat wait() until game:GetService("TeleportService")
game:GetService("TeleportService").CustomizedTeleportUI = true

There is no output. Please do not ask.