Serial doesn't work with latest mbed-os library and Hexiwear

Mbed OS
1

The following code, using the latest mbed-os library, does not work with Hexiwear :

#include "mbed.h"

Serial pc(USBTX, USBRX);

int main()
{
pc.printf(“debug\n”);

while(1);
}

The example posted here: https://os.mbed.com/teams/Hexiwear/code/Hexi_Serial_Example/ works perfectly (it uses an old version of mbed-os 5).

I am using CoolTerm and the settings are ok.

Thanks.