How to use unzip with Ant?

Hello!

(I guess this is not the correct topic, but I hope you guys excuse me)

I got a jar file (myjar.jar) with som inner folders like:
abc
def
ghi

I need to extract just the folder "def" (and all subfolders and files of course).

I have tried:
    <target name="extract_folder">
        <unzip src="lib/myjar.jar" dest="distribution/">
            <patternset>
                <include name="def"/>
            </patternset>
        </unzip>
    </target>
But this only gives me:
distribution/def
...where def is just an empty folder.

I just can't get it right so if you guys got any suggestions please let me know!

Best regards
Fredrik