volo create and volo less fail with .less syntax errors.

[ca0v]

From what I can tell this is valid .less syntax so why this error when create-ing?

D:\code\my-volo-responsive-app>..\node_modules\.bin\volo less
ParseError: Syntax Error on line 37 in D:\code\my-volo-responsive-app\tools\less\button-    groups.less:37:2
36   margin-left: -5px; // Offset the first child's margin
37   &:extend(.clearfix all);