CreateUnitAtLoc does not seem to work

[treedenn]

It seems all the parameters work except unit id.

How do I get a unit id from a 4-character string?
I have tried two functions, FourCC and UnitId, no success.
Calling CreateUnitAtLoc(Player(0), FourCC('hfoo'), GetPlayerStartLocationLoc(Player(0)), 0)
as a custom script works fine.

Additionally, when looking at the compiled version, FourCC has two arguments.

EDIT: When removing the first variable in the compiled FourCC function, it seems to work.
That means the compiled FourCC might be the problem.