Passing a variable list through .for loop using Less 2.6.1 is unable to compile - less

Question

I have been using a Less mixin which makes looping in Less, less verbose and is really handy: https://github.com/seven-phases-max/less.curious/
I upgraded from Less 2.6.0 to Less 2.6.1 and now the Less will not compile.
Here's the Less code:
// ............................................................
// .for
.for(#i, #n) {.-each(#i)}
.for(#n) when (isnumber(#n)) {.for(1, #n)}
.for(#i, #n) when not (#i = #n) {
.for((#i + (#n - #i) / abs(#n - #i)), #n);
}
// ............................................................
// .for-each
.for(#array) when (default()) {.for-impl_(length(#array))}
.for-impl_(#i) when (#i > 1) {.for-impl_((#i - 1))}
.for-impl_(#i) when (#i > 0) {.-each(extract(#array, #i))}
#gray-base: #000;
#gray-darker: #222;
#gray-dark: #333;
#gray: #555;
#gray-light: #777;
#gray-lighter: #eee;
#gray-type:
gray,
gray-base,
gray-dark,
gray-darker,
gray-light,
gray-lighter;
.gray-type {
// Mixin to generate the gray font colours for p tags in the font stacks.
.for(#gray-type); .-each(#name) {
.#{name} {
color: ##name;
}
}
}
Here's the expected output:
.gray-type .gray {
color: #555;
}
.gray-type .gray-base {
color: #000;
}
.gray-type .gray-dark {
color: #333;
}
.gray-type .gray-darker {
color: #222;
}
.gray-type .gray-light {
color: #777;
}
.gray-type .gray-lighter {
color: #eee;
}
After upgrading to Less 2.6.1 I get the following error:
>> SyntaxError: variable #[object Object],[object Object] is undefined in less/style.less on line 41, column 3:
>> 40 // Mixin to generate the gray font colours for p tags in the font stacks.
>> 41 .for(#gray-type); .-each(#name) {
>> 42 .#{name} {
Warning: Error compiling less/style.less Use --force to continue.
I think the problem is related to the hyphens being stripped from the variables during compilation, therefore making the variables passed though the list invalid.
Any help would be greatly appreciated.