bit datatype in 7.2.1

Hi,

I've upgraded from 7.1.3 to 7.2.1 and now I'm having problems with
the bit datatype. I used to do '0'::bit(20) to save some typing, but
it does not work anymore:
ERROR:  bit string length does not match type bit(20)

Is there a way to do it in version 7.2.1?