New Post: exited with code 1 after running wspbuilder.exe from command with the -customcas parameter

I try to run the following Post-build event command:

cd $(ProjectDir)
"C:\Program Files (x86)\WSPTools\WSPBuilderExtensions\WSPBuilder.exe" -WSPName $(ProjectName).wsp -CustomCAS C:\CasPolicy.txt

I got the error exited with code 1.

When I remove this from the command "-CustomCAS C:\CasPolicy.txt" it works fine and generates a wsp file in the root of my project.

Does someone know how I can run this customcas parameter?