renameFile in GHC 6.0 (Windows)

I noticed that renameFile in the Directory module in GHC 6.0 on Windows (NT 4 
Workstation; sorry, I didn't check the service pack) throws an error when a 
file already exists in the new FilePath (sorry again, I can't remember the 
exact error). The Report (& GHC documentation) say that "If the new object 
already exists, it is atomically replaced by the old object", and that 
behaviour seems to be implemented correctly by GHC 6.0 on Linux.