Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpbb/epv dev-master -> satisfiable by phpbb/epv[dev-master]. - phpbb/epv dev-master requires nikic/php-parser ~3.0 -> found nikic/php-parser[v3.0.0, ..., v3.1.5] but the package is fixed to v4.17.1 (lock file version) by a partial update and that version does not match. Make sure you list it as an argument for the update command. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.