Torch thread serialization of tables with custom metatables

test_thread_metatable.lua

-- Create table with metatable
tab = {}
idx = {a = 1}
setmetatable(tab, {__index = idx})
-- Setup threads
threads = require 'threads'
threads.Threads.serialization('threads.sharedserialize') -- Commenting this does not affect the outcome
pool = threads.Threads(2)
-- Prepare job
do
    -- Setup upvalues
    local tab_up = tab
    local tab_mt_up = getmetatable(tab)
    -- Add job
    pool:addjob(function()
        print("T1: tab_up.a (before setmetatable): " .. tostring(tab_up.a)) -- nil
        setmetatable(tab_up, tab_mt_up)
        print("T1: tab_up.a (after setmetatable): " .. tostring(tab_up.a)) -- 1
    end)
end
-- Clean exit
pool:synchronize()