WoWInterface - How to disable arena frames in 10.0?

Hey,

So I made an addon that would hide arena frames in arenas, but show them in battlegrounds.

This has since stopped working as of 10.0, and I can't figure out why or how to fix it.

Would appreciate any insight, here's the code:

Code:

local frame = CreateFrame("Frame")

frame:RegisterEvent("PLAYER_ENTERING_WORLD")

frame:RegisterEvent("ZONE_CHANGED_NEW_AREA")

frame:SetScript("OnEvent", function()

    local instanceType = select(2, IsInInstance())

    if instanceType == "arena" then

        SetCVar('showArenaEnemyFrames', 0, 'SHOW_ARENA_ENEMY_FRAMES_TEXT')

    elseif instanceType == "pvp" then

        SetCVar('showArenaEnemyFrames', 1, 'SHOW_ARENA_ENEMY_FRAMES_TEXT')

    end

end)

Even just setting the CVar manually without the addon doesn't work

Thanks