G4 error, Did you forget to signal async completion?

I just switched to Gulp version 4, everything works fine except my useref task giving me error:
```
The following tasks did not complete: dependencies-admin
Did you forget to signal async completion?
```
If I remove the useref pipe it works perfectly fine
```
gulp.task('dependencies-admin', function (done) {

return gulp.src(['app/view/admin/admin-index.php'], {base: '.'})

.pipe(useref({searchPath: '.'})) // if I comment this line the error goes away

.pipe(gulp.dest(destination));

});
```

for some reason `useref` is not signalling the end of it's task? have you tested it with G4? Am I missing something here?