Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires ibexa/solr 5.0.x-dev -> satisfiable by ibexa/solr[5.0.x-dev (alias of dev-main)]. - ibexa/solr dev-main requires ibexa/core ~5.0.x-dev -> satisfiable by ibexa/core[dev-main, 5.0.x-dev (alias of dev-main)] from composer repo (https://repo.packagist.org) but ibexa/core is the root package and cannot be modified. See https://getcomposer.org/dep-on-root for details and assistance. - ibexa/solr 5.0.x-dev is an alias of ibexa/solr dev-main and thus requires it to be installed too.