Invalid byte stream for ZipExporter

Alpha13 generates an incorrect byte stream for a ResourceAdapterArchive; the resulting archive gives:

java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(ZipFile.java:114)
at java.util.zip.ZipFile.<init>(ZipFile.java:75)
at sun.tools.jar.Main.list(Main.java:979)
at sun.tools.jar.Main.run(Main.java:224)
at sun.tools.jar.Main.main(Main.java:1149)

Alpha12 works as expected.