Unable to unzip the generated archive

When downloading the generated zip file und unziping it, I get the following error:

```
[foo@bar test]$ unzip foo.zip
Archive: foo.zip
End-of-central-directory signature not found. Either this file is not
a zipfile, or it constitutes one disk of a multi-part archive. In the
latter case the central directory and zipfile comment will be found on
the last disk(s) of this archive.
unzip: cannot find zipfile directory in one of foo.zip or
foo.zip.zip, and cannot find foo.zip.ZIP, period.
```