Trying to stop a player from entering The End

[TheMostAlienated]

So I am a Skripter for a server where we heavily lean on lore and storytelling, and I need to code a feature for one scene where basically the character is not allowed to go through the end portal. My problem however is that for some reason, even though "end portal" is listed in the documentation as a valid teleport cause, the parser still spits out an error saying that I can't compare a teleport cause to an item type. What should I do?

#make Allan not be able to go through into The End
on teleport:
    event-player's tab list name is "AlienoidTv"
    teleport cause is an end portal
    send action bar "<red>The ministry of communications and transport has revoked your access to the dimensional gates" to the event-player
    cancel event

 

[SebyHas]

on teleport:
    set {_reason} to "end portal" parsed as teleport cause
    if teleport cause contain {_reason}:
        send "ZzZ" to player