does the code violate the Liskov Substitution Principle?

I'm having a bit of a hard time trying to understand the Liskov Substitution Principle and was wondering if the following code violates the Liskov Substitution Principle?

public class Task {

     String status = "Ready"; // One of "Ready", "Started", and "Closed"

     public void setStatus(String newStatus) {
          status = newStatus;
     }
     public void cancel() {
          status = "Closed";
     }
}
public class ProjectTask extends Task {

     @Override
     public void cancel() {
          if (status.equals("Started")) {
               throw new RuntimeException("Cannot cancel a started project task.");
          }

          super.cancel();
     }
}

I think it does since the subclass doesn't behave like the base class when it is substituted and also because it throws a RunTimeException?

I'm not entirely sure and was wondering if my assumption was correct