Installation of loose pack throws EndOfFileException

During the installation of loose pack a EOFileException is thrown.
This happens if there are multiple filesets for different os like the following pack:

<pack name="MyPack" id="my.pack.id" required="yes" preselected="yes" loose="true">
<description/>
<fileset dir="../resources/win32" targetdir="$INSTALL_PATH/lib">
<os family="windows" arch="x86"/>
<include name="**"/>
</fileset>
<fileset dir="../resources/win64" targetdir="$INSTALL_PATH/lib">
<os family="windows" arch="amd64"/>
<include name="**"/>
</fileset>
</pack>

The effective problem is created during compile of the pack. If it is a file of loose pack the file size is not set to zero.
During installation of such a file we try to skip n bytes of the inputStream (see Unpacker.java:141) but the file is not included in the stream.