fern generate throwing error

[frozenmafia]

luffy@predator:~/fern/instaclone$ fern generate
/usr/local/lib/node_modules/fern-api/bundle.cjs:6001
            allowUnknownKeys: (opts == null ? void 0 : opts.allowUnknownKeys) ?? false
                                                                               ^

SyntaxError: Unexpected token '?'
    at wrapSafe (internal/modules/cjs/loader.js:915:16)
    at Module._compile (internal/modules/cjs/loader.js:963:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)
    at Module.load (internal/modules/cjs/loader.js:863:32)
    at Function.Module._load (internal/modules/cjs/loader.js:708:14)
    at Module.require (internal/modules/cjs/loader.js:887:19)
    at require (internal/modules/cjs/helpers.js:74:18)
    at Object.<anonymous> (/usr/local/lib/node_modules/fern-api/cli.cjs:3:1)
    at Module._compile (internal/modules/cjs/loader.js:999:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)