IRQ on SW Exp. Board, got stack overflow

[joaquin]

Defined Callback on SW P10 on Exp. Board:

def CallbackP10():
pinP9.toggle()

pinP10=machine.Pin('P10', mode=machine.Pin.IN, pull=machine.Pin.PULL_UP)
pinP10.irq(trigger=machine.Pin.IRQ_FALLING, handler=CallbackP10)
pinP9=machine.Pin('P9', mode=machine.Pin.OUT, pull=machine.Pin.PULL_UP)

uncaught exception inside irq handler

TypeError:

ERROR A stack overflow in taskIDLEhas been detected.