lessc - SyntaxError in global.less

While compiling as in the manual described, less throws an error in global.less

lessc styles/styles.less > styles/styles.css

SyntaxError: expected ')' got 'r' in {RootOfRoundcube}/skins/elastic/styles/global.less on line 12, column 10:

12 @import (reference) "variables";
13 @import (reference) "mixins";

Downloaded the files from roundcube.net and upgraded from RC1 to the latest version (1.4). Didn't changed the file and also _styles.less and _variables.less is empty.

lessc 1.4.2 (LESS Compiler) [JavaScript]

[alecpl]

I'm using lessc 1.6.3 and it works. So, I guess you need a newer version. I'll try to find out what is the minimal version and put it into the README file.

With the newest version of lessc it works!
Thank you very much for the quick information and for editing the README for users with the same problem!

[alecpl]

@import (reference) requires lessc 1.5.0.

[alecpl]

Done.