LESS: Whitespaces in math operations

/*
 * AFAIK:
 */
@iconsize: 200px;

.my-class{
	...
	left: (@iconsize + 100px); // Okay
	left: (@iconsize+100px); // Okay
	left: (@iconsize+ 100px); // Fail
	left: (@iconsize +100px); // Fail
	top: -@iconsize* 1.2; // Doesn't give a shit
	...
}