Printf() won't work in blinky app after bootloader

[LMESTM]

The print won't be displayed in the console, when trying to add some prints to blinky example like below:

int main() {
    printf("blinky starts\r\n");
    while (true) {
        led1 = !led1;
        wait(0.5);
    }
}

We only see the prints from the bootloader:

It works ok though when changing the main to:

Serial pc(USBTX, USBRX);
int main() {
    pc.printf("blinky starts\r\n");
    while (true) {
        led1 = !led1;
        wait(0.5);
    }
}