Your requirements could not be resolved to an installable set of packages. Problem 1 - nette/application dev-master requires nette/http ^4.0 -> found nette/http[dev-master, 4.0.x-dev (alias of dev-master)] but it conflicts with your root composer.json require (^3.2). - nette/application 4.0.x-dev is an alias of nette/application dev-master and thus requires it to be installed too. - Root composer.json requires nette/application ^4.0 -> satisfiable by nette/application[4.0.x-dev (alias of dev-master)].