Extend within (reference) imported files.

Say I have three files:

// fileA.less
.test-a {
  color: red;
}

// fileB.less
@import (reference) "fileA";

.test-b {
  background-color: green;
  &:extend(.test-a all);
}

// fileC.less
@import (reference) "fileB";

.test-c {
  &:extend(.test-b all);
}

What I expect, if I compile fileC.less (comments only to aid the understanding):

// .test-a,
// .test-b,
.test-c {
  color: red;
}

// .test-b,
.test-c {
  background-color: green;
}

What I get:

.test-b,
.test-c {
  color: red;
}
.test-c {
  background-color: green;
}

.test-b leaks in!