@extend not working in multi selectors block

[alextekartik]

While this

.good { color: red; } 
.better { @extend .good; }

is correctly generated as

.good,.better { color: red; }
.better { }

If we put @extend in a block defined for multiple selectors, the second selector is ignored

.good { color: red; } 
.better,.best { @extend .good; }

should generate

.good,.better,.best { color: red; }
.better,.best { }

but it generates

.good,.better { color: red; }
.better,.best { }

interpreting wrongly the .best definition

Unit test here