Nextjs - Unexpected token "export" - reactjs

Question

I started with NextJS, before that I used React a lot.
I run the app on docker (node:18-alpine) if it makes any difference.
I have API thing that I wrote before and published as NPM module. Now I install it with yarn add sjiamnocna/renette-api, it's ok, I can use it with react.
I have file "next-app/utils/API/initapi.ts" containing
import CAPI from "renette-api"
const API = new CAPI()
API.authenticateWithName('abcdef')
API.authorizeWithKey('12345')
export default API
It gives me SyntaxError: Unexpected token 'export'
Nothing I found worked so far, any idea?
EDIT1:
Suppose it fails during the runtime (running yarn dev) because it's successfully built and served for development. The CMD tells the same thing as the browser
SyntaxError: Unexpected token 'export'
at Object.compileFunction (node:vm:352:18)
at wrapSafe (node:internal/modules/cjs/loader:1026:15)
at Module._compile (node:internal/modules/cjs/loader:1061:27)
at Object.Module._extensions..js (node:internal/modules/cjs/loader:1151:10)
at Module.load (node:internal/modules/cjs/loader:975:32)
at Function.Module._load (node:internal/modules/cjs/loader:822:12)
at Module.require (node:internal/modules/cjs/loader:999:19)
at require (node:internal/modules/cjs/helpers:102:18)
at Object.renette-api (/home/sjiamnocna/Documents/wrk/docker_test/nginxphppg/next-app/.next/server/pages/index.js:52:18)
at __webpack_require__ (/home/sjiamnocna/Documents/wrk/docker_test/nginxphppg/next-app/.next/server/webpack-runtime.js:33:42) {
page: '/'
}
I have the file in directory next to the pages directory, couldn't that cause anything?

Answer 1

Ok, the solution is "workaround".
I changed the target of my package to ES5, now it exports the old style as NextJS expects it. BUT, if you guys have some trick to make the ES6 imports work, tell me
// before
export default MyClass
// now
module.exports = default
Have a nice day