If you initialize a local variable to null, then call an await() within a try catch block, you get ClassNotFoundException on the class in which you did that, during that classes initialization.

Simply by removing the null initialization works around the issue.

  @Async
  public Task<Void> doStuff(Task<Void> otherStuff) {

    String x = null;        //bad
    //String x;             //ok

    try {
      await(otherStuff);
    } catch (Exception e) {
      throw e;
    }
    return Task.done();

  }