Debian :: Stty Command In /etc/rc.local

Using serial terminal(emulated) to connect to linux box. In order to fix row/column count I added stty command in rc.local:

Code:
stty -F /dev/ttyS0 rows 56
stty -F /dev/ttyS0 cols 110

If I add it in redhat's /etc/rc.d/rc.local - it works fine. But if I add it in debian's /etc/rc.local - it doesn't work. I checked by redirecting some output to /dev/ttyS0 - rc.local gets executed and stty commands are executed also - but for some reason rows/columns dosn't change after I login. If I execute rc.local by hand - stty commands work.

why this works on redhat but not on debian ?