Generating error

[klarnet]

A less error occured trying to build your bundle. Please paste the error below in an issue for us at http://github.com/xbreaker/plusstrap! thanks!

{"type":"Name","message":".box-sizing is undefined","filename":"plusstrap.css","index":12399,"line":448,"column":2,"extract":[" min-height: 24px; // Make inputs at least the height of their button counterpart"," .box-sizing(border-box); // Makes inputs behave like true block-level elements","}"]}