ParseError: Unrecognised input in with « DIV { width: 500px\9 } »

Parsing success with :

DIV {
    width: 500px\9;
}

ParseError: Unrecognised input in with :

DIV { width: 500px\9 }

You can found this syntax in https://maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css

[machiaveli88]

https://github.com/less/less.js/issues/1538 has been an issue for me while importing bootstrap4 css as less reference (bootstrap4 has no less dist any more).

@import (less, reference) "~bootstrap/dist/css/bootstrap.css";

 @ /node_modules/bootstrap/dist/css/bootstrap.css (line 4475, column 31)
 near lines:

   @media screen and (min-width: 0\0) {
     .progress {

This really seems like a bug, any estimate when this could get a fix @seven-phases-max @lukeapage ? Thanks!

[ekoneko]

Now DIV { left: 500px\9 } is ok, but DIV { left: -500px\9 } still failed