gulp-mocha: After upgrading to version 4 mocha tests no longer run

The program just hangs with gulp-mocha version 4:

$ gulp test-ping
2017-02-23 11:25:08.592 - info: Using "qa" environment for tests.
[11:25:08] Using gulpfile C:\Development\project\gulpfile.js
[11:25:08] Starting 'test-ping'...

Task:

const gulp = require('gulp');
const mocha = require('gulp-mocha');

gulp.task('ping-task, () => gulp
    .src(['ping-tests.js'], {read: false})
    .pipe(mocha({
        reporter: 'spec',
        timeout: 90000,,
        useColors: true
    })));

Upon downgrading to 3.0.1 all works fine.

System: Windows 10 Node: 6.10.0

Some of the relevant gulp package:

"gulp": "^3.9.1",
"gulp-cucumber": "0.0.22",
"gulp-mocha": "^4.0.1",
"gulp-webdriver": "^2.0.3",