Elixir 6.0.0 RC2 Combine error

gulpfile.js

elixir(function(mix) {
  mix
  .browserify("app.js", "public/js/app.js", "resources/assets/js")
  .combine([
    "public/js/core.js",
    "public/js/app.js",
  ]);
});

package.json

{
  "name": "project",
  "description": "project",
  "dependencies": {
      "vue": "^1.0.20"
  },
  "devDependencies": {
    "babelify": "^6.1",
    "gulp": "^3.8.8",
    "laravel-elixir": "6.0.0-1",
    "eslint": "^2.1.0",
    "eslint-config-standard": "^5.1.0",
    "eslint-plugin-promise": "^1.0.8",
    "eslint-plugin-standard": "^1.3.2"
  },
  "scripts": {
    "lint": "eslint resources/assets/js/**"
  }
}

Terminal Output

$ node -v
v5.11.0

$ npm -v
3.8.6

$ gulp
/Users/me/Code/project/node_modules/parse-filepath/index.js:8
    throw new Error('parse-filepath expects a string.');
    ^

Error: parse-filepath expects a string.
    at parse (/Users/me/Code/project/node_modules/parse-filepath/index.js:8:11)
    at GulpPaths.parse (/Users/me/Code/project/node_modules/laravel-elixir/dist/GulpPaths.js:158:56)
    at GulpPaths.output (/Users/me/Code/project/node_modules/laravel-elixir/dist/GulpPaths.js:80:32)
    at prepGulpPaths (/Users/me/Code/project/node_modules/laravel-elixir/dist/tasks/combine.js:45:76)
    at Function.<anonymous> (/Users/me/Code/project/node_modules/laravel-elixir/dist/tasks/combine.js:27:17)
    at Function.<anonymous> (/Users/me/Code/project/node_modules/laravel-elixir/dist/index.js:49:18)
    at /Users/me/Code/project/gulpfile.js:6:6
    at Elixir (/Users/me/Code/project/node_modules/laravel-elixir/dist/index.js:22:5)
    at Object.<anonymous> (/Users/me/Code/project/gulpfile.js:3:1)
    at Module._compile (module.js:413:34)

Ran into the same problem, the fix for me was to provide a second argument to the combine method to tell what file should be created as a result
mix.combine(['myscript.js'], 'app.js')