[Vala] File. copy problem

[Joss 4 <gpnet abraerp it>]

Hi,

I have got this problem on file.copy function using valide 4.0 on windows.

this is the code :
. . . .
test.copy (destBkup, FileCopyFlags.OVERWRITE, null, null);  // create backup
. . . .

When I launch the program I got this warning :

CRITICAL **: file F:/Progetti_VALA/PetBeGone/main.vala.c: line 622: 
uncaught error: Error opening file.

this error stop the execution. I mean the lines below the test.copy are 
not executed.

I think this shouldn't be because I set  FileCopyFlags.OVERWRITE. Am I 
wrong ?