LESS: 2 mixins with same properties

Question

In CSS if I want to have two classes with the same properties, I can write the following:

.class1,
.class2
{
  color:red;
}

I wish to obtain the same result for LESS Mixins, but the following code is not allowed:

.mixin1(),
.mixin2()
{
  color:red;
}

Is there a way to formally "create a mixin duplicate"?

Answer 1

Following seven-phases-max's suggestion, I can provide a more detailed answer:

Simpler (original) solution:

.class1
{
  color:red;
}

.class2 
{
  .class1;
}

that compiles into:

.class1 {
  color: red;
}
.class2 {
  color: red;
}

---

Alternatively is possible also to set an hidden mixin thanks to () after its name, used as transition step:

.hidden-mixin()
{
  color:blue;
}

.class1,
.class2
{
  .hidden-mixin();
}

that compiles into:

.class1,
.class2 
{
  color: blue;
}