Globals from Lua 4.0 files included with "dofile": possible?

[macmacy]

Hi. I've just started with lua-language-server, so excuse me if this is kind of RTFM.
I have some legacy Lua 4.0 code. You know: no modules, just .lua files loaded with "dofile".
When I have a e.g. modulefun function in mymodule.lua, which I load in main.lua with dofile("mymodule"), lua-server gives "Undefined global 'modulefun' on modulefun(param) function call (when in main.lua file in editor).
Kind of no surprise, as lua-language-server docs state clearly it supports Lua >=5, so I can imagine it handles "require" rather than "dofile".
BUT, I've noticed that if I add this to .luarc.json:

{
    "workspace.library": ["c:/mylualib/"],
    "hint.enable": true
}

(where c:/mylualib/ is directory where my mymodule.lua is located) then, lua-language-server properly displays parameters hints on modulefun call, but still says "Undefiled global" for this function.
This proves language server knows SOMETHING about included file as it displays hints, but still considers functions from it "Undefined globals". Any recipe to have it working with Lua 4?