serial_set_parity(serial, PARITY_ODD) fails on RaspiPi3 B+

[pezi]

Running the serial test on a RaspiPi3 B+ fails

pi@raspberrypi:~/c-periphery/build $ ./test_serial /dev/serial0
..
[ OK ]  /home/pi/c-periphery/tests/test_serial.c test_open_config_close():92  serial_set_parity(serial, PARITY_ODD) == 0
 [ OK ]  /home/pi/c-periphery/tests/test_serial.c test_open_config_close():93  serial_get_parity(serial, &parity) == 0
 [FAIL]  /home/pi/c-periphery/tests/test_serial.c test_open_config_close():94  parity == PARITY_ODD
test_serial: /home/pi/c-periphery/tests/test_serial.c:94: test_open_config_close: Assertion `r' failed.

serial_set_parity() doesn't change the parity to PARITY_ODD

Serial description: Serial (fd=9, baudrate=9600, databits=7, parity=none, stopbits=1, xonxoff=false, rtscts=false, vmin=0, vtime=0.0)

Any idea?

[pezi]

Ups - my fault - didn't performed

$ echo "dtoverlay=pi3-disable-bt" | sudo tee -a /boot/config.txt
$ sudo systemctl disable hciuart
$ sudo reboot

I enabled the serial interface via raspi-config - but this seems not to be enough