Promise not returned on drain

[alexu84]

My code is something like:

request({ method: 'GET', url: url, qs: qs })
    .pipe(parse)
    .pipe(transform)
    .pipe(db)
    .on('finish', () => { r.getPool().drain(); });

I receive this Warning:

Warning: a promise was created in a handler at Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/writable_stream.js:124:7 but was not returned from it, see http://goo.gl/rRqMUw
    at new Promise (/Users/alex/Projects/turismatic-flights-static-import/node_modules/bluebird/js/release/promise.js:77:14)
    at tryOnImmediate (timers.js:534:15)
    at processImmediate [as _immediateCallback] (timers.js:514:5)
From previous event:
    at Pool.drain (/Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/pool.js:376:11)
    at Object.module.exports.init.close (/Users/alex/Projects/turismatic-flights-static-import/lib/lib.js:17:17)
    at WritableStream.<anonymous> (/Users/alex/Projects/turismatic-flights-static-import/lib/import.js:14:11)
    at emitNone (events.js:85:20)
    at WritableStream.emit (events.js:179:7)
    at finishMaybe (_stream_writable.js:481:14)
    at afterWrite (_stream_writable.js:355:3)
    at onwrite (_stream_writable.js:345:7)
    at WritableState.onwrite (_stream_writable.js:89:5)
    at /Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/writable_stream.js:124:7
From previous event:
    at WritableStream._insert (/Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/writable_stream.js:115:72)
    at WritableStream._next (/Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/writable_stream.js:83:14)
    at Immediate._onImmediate (/Users/alex/Projects/turismatic-flights-static-import/node_modules/rethinkdbdash/lib/writable_stream.js:89:16)
    at tryOnImmediate (timers.js:534:15)
    at processImmediate [as _immediateCallback] (timers.js:514:5)