del.sync(...).then is not a function

[GaziTaufiqIslam]

When I run gulp clean it gives me the following error:

TypeError: del.sync(...).then is not a function at Gulp.<anonymous> (F:\UEM\dev\ureckon19-website - Copy\gulpfile.js:85:27) at module.exports (F:\UEM\dev\ureckon19-website - Copy\node_modules\orchestrator\lib\runTask.js:34:7) at Gulp.Orchestrator._runTask (F:\UEM\dev\ureckon19-website - Copy\node_modules\orchestrator\index.js:273:3) at Gulp.Orchestrator._runStep (F:\UEM\dev\ureckon19-website - Copy\node_modules\orchestrator\index.js:214:10) at Gulp.Orchestrator.start (F:\UEM\dev\ureckon19-website - Copy\node_modules\orchestrator\index.js:134:8) at C:\Users\farhana\AppData\Roaming\npm\node_modules\gulp\bin\gulp.js:129:20 at process._tickCallback (internal/process/next_tick.js:61:11) at Function.Module.runMain (internal/modules/cjs/loader.js:744:11) at startup (internal/bootstrap/node.js:285:19) at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)

Although it returns an error yet the dist folder is deleted.

[EnzoBatista]

@GaziTaufiqIslam have you already solved it?
You might use a callback function something like that:

gulp.task('clean:dist', function(done) {
del.sync('dist');
done();
})

gulp.task('build', function (done) {
runSequence(
'clean:dist',
'sass', 'useref', 'images', 'fonts'
), done();
})