TMS320F28035: Watchdog interrupt

I have a tricky bug that is not reproducible in a larger project.
The reset source is a watchdog reset.

I have seen in the user guide (page: 87) that I can configure the watchdog to call an interrupt and not just perform a reset. I would like to use this to analyse the stack to perhaps get an idea of where the problem is.

I have inserted the line in the init routine for this:

SysCtrlRegister.SCSR.AsWord = 0x02; //  Items.WD_ENINT = 1; // enable Watchdog interrupt

static void InitWatchDog(void)
{
  EALLOW();

  // Setup WatchDog
  // set check bits and set prescale to max, set disable to 0 (enable watchdog),
  // keep WDFLAG bit as is
  // Watchdog period is set to Oscillator Cycletime (10MHz, 100nsec) * 512 * 64 * 256
  //                          = 100 nsec * 512 * 64 * 256 = 851.97 msec
  // 512: osc divide, 64: wd prescaler (max, used here), 256: 8-bit WD counter, 6: PLL multiplier (WD runs at ext. Clk rate)
  // -> WD decrements every 512*64*6 = 32768*6 = 196608 cycles
  Watchdog.WDCR.AsWord = (WDCHK_MASK | WDPS_512_64);
  SysCtrlRegister.SCSR.AsWord = 0x02; //  Items.WD_ENINT = 1; // enable Watchdog interrupt
  EDIS();
}

The debugger shows the value 0x07 for SYSCTRL.SCSR, which seems to be correct.

For testing the interrupt, i call an method with infinte loop after some secs. 

But now nothing happed, not even a reset.

i checked every ISR (also NOTUSED and NMI_ISR), but non of them is called.

I think I'm missing some enable, but I don't know which one

Please help. Thanks