Don't want to return anything from my scala function , how to do it?

Question

The scenario is like this I have a function abc() with return type of Future[Unit] now somehow inside this function I call another function xyz() which returns up a Future[List[String]] and eventually this function xyz() is only and last call inside my function abc() but as per the scala concept function returns whatever the last statement returns , so due to this I am getting a return mismatch error . What are the different ways to avoid it , I know about one way but that don't looks feasible to be as it increases 2-3 LOC.

abc():Future[Unit]={
   for{
        _ <- xyz()
     }
   yield()

}

In this way it was not giving an error at least, please also help me understand how for loops handles this futures correctly