8kHz Arduino UNO interrupt timer

#define PIN_SPK     9
bool on = false;

ISR(TIMER2_COMPA_vect) {
    //Esto se ejecuta a 8kHz
    digitalWrite(PIN_SPK, on);
    on = !on;
}

void setup(void) {
    cli();
    //set timer2 interrupt at 8kHz
    TCCR2A = 0;// set entire TCCR2A register to 0
    TCCR2B = 0;// same for TCCR2B
    // set timer count for 8khz increments
    OCR2A = 249;// = (1/8000) / ((1/(16*10^6))*8) - 1
    // turn on CTC mode
    TCCR2B |= (1 << WGM12);
    // Set CS20 bit for 1 prescaler
    TCCR2B |= 1;      //no prescale
    // enable timer compare interrupt
    TIMSK2 |= (1 << OCIE2A);
    sei();
}