Gulp AssertionError [ERR_ASSERTION]: Task function must be specified
I just run into the same problem while upgrading to gulp 4. The depending tasks have to be specified as series or in parallel, just the name is not enough anymore. Example gulp.task(‘copy’, [‘sass-min’], function() { Becomes gulp.task(‘copy’, gulp.series(‘sass-min’), function() { gulp.parallel can also be used to execute the tasks in parallel