Comma separated rule not expanded into multiple with different values

[MadLittleMods]

Input

:root {
  --color: blue;
}

.my-theme {
  --color: red;
}

:root,
.my-theme {
  a {
     color: var(--color);
  }
}

Output:

:root,
.my-theme {
  a {
     color: red;
  }
}

Expected:

:root {
  a {
     color: blue;
  }
}

.my-theme {
  a {
     color: red;
  }
}