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(at)greatgulfhomes(dot)com