Millis stop counting when using timer1 on ATTINY84

Hi have a serial TX implementation using Timer1 as the way to flip the port, it works quite well, BUT
for some reason the Millis function does not work anymore, it does not count.

As I understood it, it should be using timer0, flip over interrupt, but I must be wrong.

I uses the lates Arduino IDE, with board support from this forum

This is the code for timer1 setup

void setupSerial()
{
// set TX pin as output
DDRB = (1 << pinTX);

// set up timer1:
cli();
// 16 bit timer
// Divide by 1
TCCR1B |= (1<<CS10);
// Count cycles - (1/9600)*8000000
OCR1A = 833;
// Put Timer/Counter1 in CTC mode
TCCR1B |= 1<<WGM12;
// set interrupt flag
TIMSK1 |= 1<<OCIE1A;
sei();
}

Br.
Michael