Babel 6 regeneratorRuntime is not defined

I’m trying to use async/await from scratch on Babel 6, but I’m getting regeneratorRuntime is not defined.

.babelrc file

{
    "presets": [ "es2015", "stage-0" ]
}

package.json file

"devDependencies": {
    "babel-core": "^6.0.20",
    "babel-preset-es2015": "^6.0.15",
    "babel-preset-stage-0": "^6.0.15"
}

.js file

"use strict";
async function foo() {
  await bar();
}
function bar() { }
exports.default = foo;

Using it normally without the async/await works just fine. Any ideas what I’m doing wrong?