Default value for bit datatype

When I try to do a default value for the bit datatype, eg:
CREATE TABLE my_calendar (
 ID serial NOT NULL ,
 Global_field bit DEFAULT 0 NOT NULL ,
)

I get the message:
ERROR:  Attribute 'global_field' is of type 'bit' but default expression
is of type 'int4'
        You will need to rewrite or cast the expression

I have tried (bit) 0, bit(0), bit 0, etc but have not found a way to do
casting.  Can anyone help me to set a default value for a bit datatype
field?

Thanks

Terry Fielder
terry@greatgulfhomes.com