Lua 5.3 unable to convert cdata to string

Using RandomKit with lua 5.3 generate this error in file randomkit/wrapC.lua:193.
when executed in the following file:
`require 'randomkit'
torch.getRNGState()`
Changing line 193 from:
'local clonedState = ffi.string(randomkit._state, ffi.sizeof(randomkit._state))'
to
`local clonedState = randomkit._state, ffi.sizeof(randomkit._state)`
correct the problem however I have no idea of the implication of the change on other system and other lua system.