Subject EConvert error when passing to storedprocs?

I am trying to run this stored procedure (simplified):
UPDATE abc SET abc.z=:IntParam

(z and IntParam are declared as integers) and all is fine. But then
when I try in delphi to pass it a parameter like this:


and then execute it I get an EConvert error because "-" is not a
valid integer !

Where did my logic go wrong ?? :-(