pristine-tar and upstream zip

[Felix Natter <fnatter@gmx.net>]

hi,

as far as I understand Debian packaging, the .orig.tar.{gz,bz2} shall
have the same checksum as the original upstream tarball (by using
pristine-tar). This worked for me when the upstream tarball is *.tar.gz,
but in a package libidw-java, where the upstream tarball is *.zip, this
does not seem to work:

$ md5sum .../idw-gpl-1.6.1-src.zip 
2c080a59049a4de93497106d89cc59e3  .../idw-gpl-1.6.1-src.zip

$ md5sum *orig*
a9a19163194f6fb5c58a44a3c1c251f4  libidw-java_1.6.1.orig.tar.bz2

Here is how I imported the sources:
$ git-import-orig -u1.6.1 --pristine-tar .../idw-gpl-1.6.1-src.zip
What will be the source package name? [] libidw-java
gbp:info: Importing '/home/felix/Freeplane-Debian-Package/libidw-java_1.6.1.orig.tar.bz2' to branch 'upstream'...
gbp:info: Source package is libidw-java
gbp:info: Upstream version is 1.6.1
pristine-tar: committed libidw-java_1.6.1.orig.tar.bz2.delta to branch pristine-tar
gbp:info: Merging to 'master'
gbp:info: Successfully imported version 1.6.1 of /home/felix/Freeplane-Debian-Package/libidw-java_1.6.1.orig.tar.bz2

And here is how I built:
$ git-buildpackage -us -uc --git-ignore-new --git-pristine-tar
dh clean --with javahelper
   dh_testdir
   dh_auto_clean
   jh_clean
   dh_clean
pristine-tar: successfully generated /home/felix/debiantmp/idw/libidw-java_1.6.1.orig.tar.bz2
[...]

=> I guess the pristine-tar difference is built against the .tar.bz2,
not against the zip. So is it possible/required that the zip has the 
same checksum as the orig.tar.bz2?

Thanks and Best Regards,
-- 
Felix Natter