Less language is an extension of css and less4j compiles it into regular css. Less adds several dynamic features into css: variables, expressions, nested rules, and so on. Less was designed to be compatible with css and any correct css file is also correct less file.
Less.js issue: https://github.com/less/less.js/issues/ 2743 Pull request: https://github.com/less/less.js/commit/ bcc8ced8b0105c44073a823f441d1fb297697f41