QWaitCondition: Destroyed while threads are still running

i have two threads: one - gui & other - backgroud.
in gui thread i have pointer to other thread.
when closing app gui destructor is called, i want to quit & destroy other thread there:

Code:

---

delete pOther;

---

other's destructor look like this:

Code:

---

other::~other()
{
   if ( isRunning() )
      quit();
   wait();
}

---

but qt-4.6.1 prints warning QWaitCondition: Destroyed while threads are still running.
there is now warnings neither in qt-4.6.0 nor in qt-4.3.1 on windows.
whats wrong? is it my mistake? how to get rid of it? thanks