LESS CSS compilation error on subtracting color values -

LESS CSS compilation error on subtracting color values -

i'm running lessc my.less my.css.

code:

@background: #343434; input[type='text'] { border: 1px solid (@background-#222); }

fails providing error

nameerror: variable @background- undefined in ...

however,

input[type='text'] { border: 1px solid (@background+#222); }

will work.

i have read bom, not case. have checked less compiler installed latest nodejs. tried #222222. out of ideas.

the - may part of identifier. why tells can't find variable @background-. on other hand + never part of identifier , less knows variable @background. have insert space working:

input[type='text'] { border: 1px solid (@background -#222); }

colors compilation less subtract