Thread:Extension talk:Semantic MediaWiki/Installation. MW 1.25

I installed Mediawiki 1.25.1 (new empty DB, no extensions). I run the installation script for SMW (https://www.semantic-mediawiki.org/wiki/Help:Installation/Using_Composer_with_MediaWiki_1.22%2B)


 * 1) > composer.phar require mediawiki/semantic-media-wiki "~2.1"

The composer reports: [RuntimeException] The lock file does not contain require-dev information, run install with the --no-dev option or run update to install those packages.

What am I doing wrong?